AAT2550

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Document overview

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• PDF pages: 34

Technical content

Features

• Two Step-Down Converters: ▪ 600mA Output Current per Converter ▪ V IN Range: 2.7V to 5.5V ▪ 1.4MHz Switching Frequency ▪ Low R DS(ON) 0.4 Integrated Power Switches ▪ Internal Soft Start ▪ 27 μA Quiescent Current per Converter
• Highly Integrated Battery Charger: ▪ Programmable Charging Current from 100mA to 1A ▪ Pass Device ▪ Reverse Blocking Diodes ▪ Current Sensing Resistor ▪ Digital Thermal Regulation
• Short-Circuit, Over-Temperature, and Current Limit Protection
• QFN44-24 Package
• -40°C to +85°C Temperature Range

Applications

• Cellular Telephones
• Digital Cameras
• Handheld Instruments
• MP3, Portable Music, and Portable Media Players
• PDAs and Handheld Computers Typical Application AAT2550 Adapter Serial Interface STAT1 STAT2 ADPSET DATA ENBAT INA INB Li-Ion Battery or Adapter BAT TS CT Batt+ Batt- Temp Battery Pack LXA COUTA FBA VOUTA RSET LXB COUTB FBB VOUTB ENA ENB GND ADP

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Pin Descriptions Pin # Symbol Function 1 ENA Enable pin for Converter A. When connected to logic low, it disables the step-down converter and con- sumes less than 1μA of current. When connected to logic high, the converter operates normally. 2 LXA Power switching node for Converter A. Connect the inductor to this pin. Internally, it is connected to the drain of both high- and low-side MOSFETs. 3, 17 PGND Power ground. Connect the PGND pins together as close to the IC as possible. Connect AGND to PGND at a single point as close to the IC as possible. 4 DATA Status report to the microcontroller via serial interface (open drain). 5, 7 N/C Not connected. 6 ADPSET Charge current set point. Connect a resistor from this pin to ground. Refer to Typical Characteristics curves for resistor selection. 8 BAT Battery charging and sensing. Connect the positive terminal of the battery to BAT. 9 ADP Input for adapter charger. 10, 11, 22 AGND Analog signal ground. Connect AGND to PGND at a single point as close to the IC as possible. 12 ENBAT Enable pin for the battery charger. When connected to logic low, the battery charger is disabled and con- sumes less than 1μA of current. When connected to logic high, the charger operates normally. 13 TS Temperature sense input. Connect to a 10k  NTC thermistor. 14 STAT2 Battery charge status indicator pin to drive an LED. It is an open drain input. 15 STAT1 Battery charge status indicator pin to drive an LED. It is an open drain input. 16 CT Timing capacitor to adjust internal watchdog timer. Sets maximum charge time for adapter powered trickle, constant current, and constant voltage charge modes. 18 LXB Power switching node for Converter B. Connect the inductor to this pin. Internally, it is connected to the drain of both high- and low-side MOSFETs. 19 ENB Enable pin for Converter B. When connected to logic low, it disables the step-down converter and con- sumes less than 1μA of current. When connected to logic high, the converter operates normally. 20 INB Input voltage for Converter B. 21 FBB Output voltage feedback input for Converter B. FBB senses the output voltage B for regulation control. The FBB regulation threshold is 0.6V. A resistive voltage divider is connected to the output B, FBB, and AGND. 23 FBA Output voltage feedback input for Converter A. FBA senses the output voltage A for regulation control. The FBA regulation threshold is 0.6V. A resistive voltage divider is connected to the output A, FBA, and AGND. 24 INA Input voltage for Converter A. EP Exposed paddle; connect to ground directly beneath the package. Pin Configuration QFN44-24 (Top View) ENA LXA PGND DATA N/C ADPSET N/C BAT ADP AGND AGND ENBAT STAT1 CT STAT2 TS PGND LXB ENB INB FBB AGND FBA INA

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Absolute Maximum Ratings1 Symbol Description Value Units VINA/B, VADP INA, INB, and ADP Voltages to GND -0.3 to 6.0 V VLXA/B, VFBA/B VLXA, VLXB, VFBA, and VFBB to GND -0.3 to V INA/B, VADP + 0.3 V VX Voltage on All Other Pins to GND -0.3 to 6.0 V TJ Operating Junction Temperature Range -40 to 150 °C TLEAD Maximum Soldering Temperature (at leads, 10 sec) 300 °C Thermal Information Symbol Description Value Units PD Maximum Power Dissipation 2.0 W JA Thermal Resistance2 50 °C/W 1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at co nditions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time. 2. Mounted on an FR4 printed circuit board.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Electrical Characteristics1 VIN = 3.6V; TA = -40°C to +85°C, unless otherwise noted. Typical values are at T A = 25°C. Symbol Description Conditions Min Typ Max Units Step-Down Converters A and B VIN Input Voltage 2.7 5.5 V VUVLO Under-Voltage Lockout Threshold VIN Rising 2.7 V Hysteresis 100 mV V IN Falling 1.8 V VOUT Output Voltage Tolerance I OUT = 0 to 600mA, VIN = 2.7V to 5.5V -3.0 3.0 % VOUT Output Voltage Range 0.6 V IN V IOUT Output Current Per Converter 600 mA IQ Quiescent Current Each Converter 27 70 μA ISHDN Shutdown Current V ENA = VENB = GND 1.0 μA ILIM P-Channel Current Limit Each Converter 0.8 1.0 A ILX_LEAK LX Leakage Current V IN = 5.5V, VLX = 0 to VIN, VENA = VENB = GND 1.0 μA IFB_LEAK Feedback Leakage V FB = 0.6V 0.2 μA RFB FB Impedance V OUT > 0.6V 250 k  VFB Feedback Threshold Voltage Accuracy (0.6V Adjustable Version) No Load, TA = 25°C 0.591 0.6 0.609 V RDS(ON)H High-Side Switch On Resistance 0.45  RDS(ON)L Low-Side Switch On Resistance 0.40  VLineReg Line Regulation V IN = 2.7V to 5.5V 0.1 %/V FOSC Switching Frequency 1.4 MHz TSD Over-Temperature Shutdown Threshold 140 °C THYS Over-Temperature Shutdown Hysteresis 15 °C VEN(L) Enable Threshold Low 0.6 V VEN(H) Enable Threshold High 1.4 V IEN Input Low Current V IN = VFB = 5.5V -1.0 1.0 μA 1. The AAT2550 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assu red by design, characterization, and correla- tion with statistical process controls.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Electrical Characteristics1 (continued) VADP = 5V; TA = -40°C to +85°C, unless otherwise noted. Typical values are at T A = 25°C. Symbol Description Conditions Min Typ Max Units Battery Charger VADP Adapter Voltage Range 4.0 5.5 V VUVLO Under-Voltage Lockout Rising Edge 3.0 V UVLO Hysteresis 150 mV IQ Quiescent Current I CHARGE = 100mA 0.75 3.0 mA ISLEEP Sleep Mode Current V BAT = 4.25V 0.3 1.0 μA ILEAKAGE Reverse Leakage Current V BAT = 4V, ADP Pin Open 1.0 μA ISHDN Shutdown Current V EN = GND 1.0 μA VBAT_EOC2 End of Charge Voltage Accuracy 4.158 4.2 4.242 V VCH/VCH Output Charge Voltage Tolerance 0.5 % VMIN Preconditioning Voltage Threshold 2.80 3.0 3.15 V VRCH Battery Recharge Voltage Threshold V BAT_EOC - 0.1 V ICH Charge Current 100 1000 mA ICH/ICH Charge Current Regulation Tolerance 10 % VADPSET ADPSET Pin Voltage Constant Current Mode 2.0 V KIA Current Set Factor: ICH/IADPSET 4000 RDS(ON) Charger Pass Device V IN = 5.5V 0.20 0.25 0.35  TC Constant Current Mode Time-Out C T = 100nF, VADP = 5.5V 3.0 Hour TP Preconditioning Time-Out C T = 100nF, VADP = 5.5V 25 Minute TV Constant Voltage Mode Time-Out C T = 100nF, VADP = 5.5V 3.0 Hour VSTAT Output Low Voltage I SINK = 4mA 0.4 V ISTAT STAT Sink Current 8.0 mA VOVP Over-Voltage Protection 4.4 V ITK/ICH Preconditioning (Trickle Charge) Current 10 % ITERM/ICH Charge Termination Threshold Current 7.5 % ITS Current Source from TS Pin 70 80 90 μA TS1 TS Hot Temperature Fault Threshold 310 330 350 mVHysteresis 15 TS2 TS Cold Temperature Fault Threshold 2.2 2.3 2.4 V Hysteresis 10 mV IDATA DATA Pin Sink Current DATA Pin is Active Low 3.0 mA VDATA(H) Input High Threshold 1.6 V VDATA(L) Input Low Threshold 0.4 V SQPULSE Status Request Pulse Width 200 ns TPeriod System Clock Period 50 μs FDATA Data Output Frequency 20 kHz TREG Thermal Loop Regulation 90 °C TLOOP_IN Thermal Loop Entering Threshold 110 °C TLOOP_OUT Thermal Loop Exiting Threshold 85 °C TSD Over-Temperature Shutdown Threshold 145 °C 1. The AAT2550 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assu red by design, characterization, and correla- tion with statistical process controls. 2. End of Charge Voltage Accuracy is specified over the 0° to 70°C ambient temperature range.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Typical Characteristics — Step-Down Converter Efficiency vs. Load (VOUT = 1.8V; L = 4.7μμH) Output Current (mA) Efficiency (%) 100 0.1 1 10 100 100 0 VIN = 2.7V VIN = 3.6V VIN = 4.2V DC Regulation (VOUT = 1.8V) Output Current (mA) Output Error (%) -1.0 -0.5 0.0 0.5 1.0 0.1 1 10 100 1000 VIN = 4.2V VIN = 3.6V VIN = 2.7V Efficiency vs. Load (VOUT = 2.5V; L = 6.8μμH) Output Current (mA) Efficiency (%) 100 0.1 1 10 100 1000 VIN = 5.0V VIN = 3.6V VIN = 4.2V VIN = 2.7V DC Regulation (VOUT = 2.5V) Output Current (mA) Output Error (%) -1.0 -0.5 0.0 0.5 1.0 0.1 1 10 100 1000 VIN = 5.0V VIN = 3.6V VIN = 3.0V VIN = 4.2V Efficiency vs. Load (VOUT = 3.3V; L = 6.8μμH) Output Current (mA) Efficiency (%) 100 0.1 1 10 100 1000 VIN = 3.6V VIN = 4.2V VIN = 5.0V DC Regulation (VOUT = 3.3V; L = 6.8µH) Output Current (mA) Output Error (%) -1.0 -0.5 0.0 0.5 1.0 0.1 1 10 100 1000 VIN = 5.0V VIN = 4.2V VIN = 3.6V

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Typical Characteristics — Step-Down Converter (continued) Soft Start (VIN = 3.6V; VOUT = 1.8V; IOUT = 400mA) Time (100μμs/div) Enable and Output Voltage (top) (V) Inductor Current (bottom) (A) 0.0 1.0 2.0 3.0 4.0 5.0 -0.4 -0.2 0.0 0.2 0.4 0.6 VEN IL VO Line Regulation (VOUT = 1.8V) Input Voltage (V) Accuracy (%) -0.40 -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40 IOUT = 10mA IOUT = 400mA IOUT = 1mA Output Voltage Error vs. Temperature (VIN = 3.6V; VO = 1.8V; IOUT = 400mA) Temperature (°°C) Output Error (%) -2.0 -1.0 0.0 1.0 2.0 -40 -20 0 20 40 60 80 100 Switching Frequency vs. Temperature (VIN = 3.6V; VOUT = 1.8V) Temperature (°°C) Variation (%) -15.0 -12.0 -9.0 -6.0 -3.0 0.0 3.0 6.0 9.0 12.0 15.0 -40 -20 0 20 40 60 80 100 Frequency vs. Input Voltage Input Voltage (V) Frequency Variation (%) -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 VOUT = 1.8V VOUT = 2.5V VOUT = 3.3V No Load Quiescent Current vs. Input Voltage Input Voltage (V) Supply Current (μμA) 85°C 25°C -40°C

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Typical Characteristics — Step-Down Converter (continued) P-Channel RDS(ON) vs. Input Voltage Input Voltage (V) RDS(ON)H (mΩΩ) 300 350 400 450 500 550 600 650 700 750 25°C 120°C 100°C 85°C N-Channel RDS(ON) vs. Input Voltage Input Voltage (V) RDS(ON)L (mΩΩ) 300 350 400 450 500 550 600 650 700 750 25°C 120°C 100°C 85°C Load Transient Response (1mA to 300mA; VIN = 3.6V; VOUT = 1.8V; COUT = 10µF; CFF = 100pF) Output Voltage (top) (V) Load and Inductor Current (200mA/div) (bottom) Time (50µs/div) 1.7 1.8 1.9 2.0 VO 300mA 1mA IO IL Load Transient Response (300mA to 400mA; VIN = 3.6V; VOUT = 1.8V; COUT = 4.7µF) Output Voltage (top) (V) Load and Inductor Current (100mA/div) (bottom) Time (50µs/div) 1.75 1.80 1.85 1.90 0.1 0.2 0.3 0.4 VO IO IL 400mA 300mA Load Transient Response (300mA to 400mA; VIN = 3.6V; VOUT = 1.8V; COUT = 10µF) Output Voltage (top) (V) Load and Inductor Current (100mA/div) (bottom) Time (50µs/div) 1.75 1.80 1.85 1.90 0.1 0.2 0.3 0.4 VO IO IL 400mA 300mA Load Transient Response (300mA to 400mA; VIN = 3.6V; VOUT = 1.8V; COUT = 10µF; CFF = 100pF) Output Voltage (top) (V) Load and Inductor Current (100mA/div) (bottom) Time (50µs/div) 1.775 1.800 1.825 1.850 0.1 0.2 0.3 0.4 VO IO IL 400mA 300mA

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Typical Characteristics — Step-Down Converter (continued) Line Response (VOUT = 1.8V @ 400mA) Output Voltage (top) (V) Input Voltage (bottom) (V) Time (25µs/div) 1.80 1.81 1.82 3.0 3.5 4.0 4.5 Output Ripple (VIN = 3.6V; VOUT = 1.8V; IOUT = 1mA) Time (10µs/div) Output Voltage (AC coupled) (top) (mV) Inductor Current (bottom) (A) -20 -0.10 -0.05 0.00 0.05 0.10 0.15 VO IL Output Ripple (VIN = 3.6V; VOUT = 1.8V; IOUT = 400mA) Time (500ns/div) Output Voltage (AC coupled) (top) (mV) Inductor Current (bottom) (A) -20 0.1 0.2 0.3 0.4 0.5 0.6 VO IL

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Typical Characteristics — Battery Charger Constant Charging Current vs. RSET RSET (kΩΩ) ICH (mA) 100 1000 10000 1 10 100 Battery Voltage vs. Supply Voltage Supply Voltage (V) VBAT (V) 4.158 4.179 4.200 4.221 4.242 End of Charge Voltage Regulation vs. Temperature Temperature (°°C) VBAT_EOC (V) 4.158 4.179 4.200 4.221 4.242 -50 -25 0 25 50 75 100 Preconditioning Threshold Voltage vs. Temperature Temperature (°°C) VMIN (V) 2.95 2.96 2.97 2.98 2.99 3.00 3.01 3.02 3.03 3.04 3.05 -50 -25 0 25 50 75 100 Preconditioning Current vs. Temperature (ADPSET = 8.06kΩΩ) Temperature (°C) ITK (mA) 100 110 120 -50 -25 0 25 50 75 100 Constant Charging Current vs. Temperature (ADPSET = 8.06kΩΩ) Temperature (°C) ICH (mA) 900 920 940 960 980 1000 1020 1040 1060 1080 1100 -50 -25 0 25 50 75 100

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Typical Characteristics — Battery Charger (continued) Charging Current vs. Battery Voltage (ADPSET = 8.06kΩΩ; VIN = 5.0V) Battery Voltage (V) ICH (A) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Constant Charging Current vs. Input Voltage (ADPSET = 8.06kΩΩ) Input Voltage (V) ICH (mA) 200 400 600 800 1000 1200 VBAT = 3.3V VBAT = 3.5V VBAT = 3.9V VIH vs. Input Voltage EN Pin (Rising) Input Voltage (V) VIH (V) 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 -40°C +25°C +85°C VIL vs. Input Voltage EN Pin (Falling) Input Voltage (V) VIH (V) 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 -40°C +25°C +85°C Adapter Mode Supply Current vs. ADPSET Resistor ADPSET Resistor (kΩΩ) IQ (mA) 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 1 10 100 1000 Pre-Conditioning Constant Current Counter Timeout vs. Temperature (CT = 0.1μμF) Temperature (°C) Counter Timeout (%) -10 -50 -25 0 25 50 75 100

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Typical Characteristics — Battery Charger (continued) CT Pin Capacitance vs. Counter Timeout Time (hours) Capacitance (μμF) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 02468 1 0 Precondition Timeout Precondition + Constant Current Timeout or Constant Voltage Timeout Temperature Sense Output Current vs. Temperature Temperature (°°C) TS Pin Current (μA) -50 -25 0 25 50 75 10

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Functional Description The AAT2550 is a highly integrated power management IC comprised of a battery charger and two step-down voltage converters. The battery charger is designed for charging single-cell lithium-ion / polymer batteries. Featuring an integrated pass device and reverse block- ing, it offers a constant current / constant voltage charge algorithm with a user-programmable charge current level. The two step-down converters have been designed to minimize external component size and maximize effi- ciency over the entire load range. Each converter has independent enable and input voltage pins and can pro- vide 600mA of load current. Battery Charger The battery charger is designed to operate with standard AC adapter input sources, while requiring a minimum number of external components. It precisely regulates charge voltage and current for single-cell lithium-ion / polymer batteries. The adapter charge input constant current level may be programmed up to 1A for rapid charging applications. The battery charger features thermal loop charge reduc- tion. In the event of operating ambient temperatures exceeding the power dissipation abilities of the device package for a given constant current charge level, the Functional Block Diagram ENB LXB Err. Amp. DH DL PGND FBB Voltage Reference Control Logic Logic ENA LXA Err. Amp. DH DL PGND FBA Voltage Reference Control Logic Logic INB Charge Control Reverse Blocking CV/Pre- Charge Constant Current Current Compare ADP BAT OTP Charge Status STAT2 STAT1 4.2V ENBAT ADPSET TS INA Window Comparator 80μAWatchdog Timer CT UVLO

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications charge control will enter into thermal regulation. When the system thermal regulation becomes active, the pro- grammed constant current charge amplitude will auto- matically decrease to a safe level for the present operat- ing conditions. If the ambient temperature drops to a level sufficient to allow the device to come out of thermal regulation, then the system will automatically resume charging at the full programmed constant current level. This intelligent thermal management system permits the battery charger to operate and charge a battery cell safely over a wide range of ambient conditions, while maximizing the greatest possible charge current and minimizing the battery charge time for a given set of conditions. Status monitor output pins are provided to indicate the battery charge state by directly driving two external LEDs. A serial interface output is also available to report any one of 12 distinct charge states to the host system microcontroller / microprocessor. Battery temperature and charge state are fully monitored for fault conditions. In the event of an over-voltage or over-temperature condition, the device will automatically shut down, pro- tecting the charging device, control system, and the bat- tery under charge. In addition to internal charge control- ler thermal protection, the charger also offers a tem- perature sense feedback function (TS pin) from the battery to shut down the device in the event the battery exceeds its own thermal limit during charging. All fault events are reported to the user either by simple status LEDs or via the DATA pin function. Charging Operation As shown in Figure 1, there are three basic phases for the battery charge cycle: 1. Pre-conditioning / trickle charge 2. Constant current / fast charge 3. Constant voltage charge Battery Preconditioning Before the start of charging, the charger checks several conditions in order to assure a safe charging environ- ment. The input supply must be above the minimum operating voltage, or under-voltage lockout threshold UVLO), for the charging sequence to begin. Also, the battery temperature, as reported by a thermistor con- nected to the TS pin from the battery, must be within the proper window for safe charging. When these conditions have been met and a battery is connected to the BAT pin, the charger checks the state of the battery. If the battery voltage is below the preconditioning voltage threshold (V MIN), then the charge control begins precon- ditioning the battery. The preconditioning trickle charge current is equal to the fast charge constant current divided by 10. For example, if the programmed fast charge current is 1A, then the preconditioning mode (trickle charge) current will be 100mA. Battery precon- ditioning is a safety precaution for deeply discharged batteries and also helps to limit power dissipation in the pass transistor when the voltage across the device is at the greatest potential. Preconditioning Trickle Charge Phase Constant Current Charge Phase Constant Voltage Charge Phase Charge Complete Voltage Constant Current Mode Voltage Threshold Regulated Current Trickle Charge and Termination Threshold I = CC / 10 I = Max CC Figure 1: Typical Charge Profile.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Fast Charge/Constant Current Charging Battery preconditioning continues until the voltage on the BAT pin exceeds the preconditioning voltage thresh- old (V MIN). At this point, the charger begins the constant current fast charging phase. The fast charge constant current (I CH) amplitude is programmed by the user via the R SET resistor. The charger remains in the constant current charge mode until the battery reaches the volt- age regulation threshold, V BAT_EOC. Constant Voltage Charging The system transitions to a constant voltage charging mode when the battery voltage reaches the output charge regulation threshold (V BAT_EOC) during the con- stant current fast charge phase. The regulation voltage level is factory programmed to 4.2V (±1%). The charge current in the constant voltage mode drops as the bat- tery under charge reaches its maximum capacity. End of Charge Cycle Termination and Recharge Sequence When the charge current drops to 7.5% of the pro- grammed fast charge current level in the constant volt- age mode, the device terminates charging and goes into a sleep state. The charger will remain in a sleep state until the battery voltage decreases to a level below the battery recharge voltage threshold (V RCH). When the input supply is disconnected, the charger will automati- cally transition into a power-saving sleep mode. Consuming only an ultra-low 0.3 μA in sleep mode, the charger minimizes battery drain when it is not charging. This feature is particularly useful in applications where the input supply level may fall below the battery charge or under-voltage lockout level. In such cases where the input voltage drops, the device will enter sleep mode and resume charging automatically once the input sup- ply has recovered from the fault condition. Step-Down Converters The AAT2550 offers two high-performance, 600mA, 1.4MHz step-down converters. Both converters minimize external component size and optimize efficiency over the entire load range. Both converters can be programmed with external feedback resistors to any voltage ranging from 0.6V to the input voltage. At dropout, the con- verter duty cycle increases to 100% and the output volt- age tracks the input voltage minus the R DS(ON) drop of the P-channel MOSFET. Input voltage range is 2.7V to 5.5V and each converter’s efficiency has been optimized for all load conditions, ranging from no load to 600mA. The internal error amplifier and compensation provides excellent transient response, load regulation, and line regulation. Soft start eliminates output voltage overshoot when the enable or the input voltage is applied. Soft Start / Enable The internal soft start limits the inrush current during start-up. This prevents possible sagging of the input voltage and eliminates output voltage overshoot. Typical start-up time for a 4.7μF output capacitor and load cur- rent of 600mA is 100μs. The AAT2550 offers independent enable pins for each converter. When connected to logic low, the enable input forces the respective step-down converter into a low-power, non-switching, shutdown state. The total input current during shutdown is less than 1μA for each channel. Current Limit and Over-Temperature Protection For overload conditions, the peak input current is limit- ed. To minimize power dissipation and stresses under current limit and short-circuit conditions, switching is terminated after entering current limit for a series of pulses. Switching is terminated for seven consecutive clock cycles after a current limit has been sensed for a series of four consecutive clock cycles. Thermal protection completely disables switching when internal dissipation becomes excessive. The junction over-temperature threshold is 140°C with 15°C of hys- teresis. Once an over-temperature or over-current fault conditions is removed, the output voltage automatically recovers. Under-Voltage Lockout The under-voltage lockout circuit prevents the device from improper operation at low input voltages. Internal bias of all circuits is controlled via the VIN input. Under-voltage lockout (UVLO) guarantees sufficient V IN bias and proper operation of all internal circuitry prior to activation.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications System Operation Flow Chart Yes Yes Yes Yes Yes Yes No No No No No No No No No Set Enable Timing Expire TERM Yes BAT_EOC

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications

Application Information

The adapter constant current charge levels can be pro- grammed up to 1A. The AAT2550 will operate from the adapter input over a 4.0V to 5.5V range. The constant current fast charge current for the adapter input mode is set by the R SET resistor connected between the ADPSET and ground. Refer to Table 1 for recommend- ed R SET values for a desired constant current charge level. The precise charging function in the adapter mode may be read from the DATA pin and/or status LEDs. Please refer to the Battery Charge Status Indication discussion in this datasheet for further details on data reporting. Thermal Loop Control Due to the integrated nature of the linear charging con- trol pass device, a special thermal loop control system has been employed to maximize charging current under all operation conditions. The thermal management sys- tem measures the internal circuit die temperature and reduces the fast charge current when the device exceeds a preset internal temperature control threshold. Once the thermal loop control becomes active, the fast charge current is initially reduced by a factor of 0.44. The initial thermal loop current can be estimated by the following equation: ITLOOP = ICH · 0.44 The thermal loop control re-evaluates the circuit die tem- perature every three seconds and adjusts the fast charge current back up in small steps to the full fast charge cur- rent level or until an equilibrium current is discovered and maximized for the given ambient temperature condition. The thermal loop controls the system charge level; there- fore, the AAT2550 will always provide the highest level of constant current possible in the fast charge mode for any given ambient temperature condition. Adapter Input Charge Inhibit and Resume The AAT2550 has an under-voltage lockout and power on reset feature so that the charger will suspend charging and shut down if the input supply to the adapter pin drops below the UVLO threshold. When power is re- applied to the adapter pin or the UVLO condition recov- ers and ADP > V BAT, the system charge control will assess the state of charge on the battery cell and will auto- matically resume charging in the appropriate mode for the condition of the battery. ICH ADP RSET (k) 100 84.5 200 43.2 300 28.0 400 21.0 500 16.9 600 13.3 700 11.5 800 10.2 900 9.09 1000 8.06 Table 1: Resistor Values. Enable / Disable The AAT2550 provides an enable function to control the charger IC on and off. The enable (ENBAT) pin is active high. When pulled to a logic low level, the AAT2550 will be shut down and forced into the sleep state. Charging will be halted regardless of the battery voltage or charg- ing state. When the device is re-enabled, the charge control circuit will automatically reset and resume charg- ing functions with the appropriate charging mode based on the battery charge state and measured cell voltage. Programming Charge Current The fast charge constant current charge level is pro- grammed with a resistor placed between the ADPSET pin and ground. The accuracy of the fast charge, as well as the preconditioning trickle charge current, is dominated by the tolerance of the set resistor used. For this reason, 1% tolerance metal film resistors are recommended for the set resistor function. Fast charge constant current levels from 100mA to 1A can be set by selecting the appropriate resistor value from Table 1. The R SET resistor should be connected between the ADPSET pin and ground.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications RSET (kΩΩ) ICH (mA) 100 1000 10000 11 0 1 0 0 ADP Figure 2: Constant Charging Current vs. R SET. Protection Circuitry Programmable Watchdog Timer The AAT2550 contains a watchdog timing circuit for the adapter input charging mode. Typically, a 0.1μF ceramic capacitor is connected between the CT pin and ground. When a 0.1μF ceramic capacitor is used, the device will time a shutdown condition if the trickle charge mode exceeds 25 minutes and a combined trickle charge plus fast charge mode of three hours. When the device tran- sitions to the constant voltage mode, the timing counter is reset and will time out after three hours and shut down the charger (see Table 2). Mode Time Trickle Charge (TC) Time Out 25 minutes Trickle Charge (TC) + Constant Current (CC) Mode Time Out 3 hours Constant Voltage (VC) Mode Time Out 3 hours Table 2: Summary for a 0.1 μF Used for the Timing Capacitor. The CT pin is driven by a constant current source and will provide a linear response to increases in the timing capacitor value. Thus, if the timing capacitor were to be doubled from the nominal 0.1 μF value, the time-out durations would be doubled. If the programmable watchdog timer function is not need- ed, it can be disabled by connecting the CT pin to ground. The CT pin should not be left floating or un-terminated, as this will cause errors in the internal timing control circuit. The constant current provided to charge the timing capacitor is very small, and this pin is susceptible to noise and changes in capacitance value. Therefore, the timing capacitor should be physically located on the printed circuit board layout as closely as possible to the CT pin. Since the accuracy of the internal timer is domi- nated by the capacitance value, 10% tolerance or better ceramic capacitors are recommended. Ceramic capacitor materials, such as X7R and X5R type, are a good choice for this application. Over-Voltage Protection An over-voltage event is defined as a condition where the voltage on the BAT pin exceeds the maximum bat- tery charge voltage and is set by the over-voltage pro- tection threshold (V OVP). If an over-voltage condition occurs, the AAT2550 charge control will shut down the device until voltage on the BAT pin drops below the over- voltage protection threshold (V OVP). The AAT2550 will resume normal charging operation after the over-volt- age condition is removed. During an over-voltage event, the STAT LEDs will report a system fault, and the actual fault condition may be read via the DATA pin signal. Over-Temperature Shutdown The AAT2550 has a thermal protection control circuit which will shut down charging functions should the inter- nal die temperature exceed the preset thermal limit threshold. Battery Temperature Fault Monitoring In the event of a battery over-temperature condition, the charge control will turn off the internal pass device and report a battery temperature fault on the DATA pin function. The STAT LEDs will also display a system fault. After the system recovers from a temperature fault, the device will resume charging operation. The AAT2550 checks battery temperature before start- ing the charge cycle, as well as during all stages of charging. This is accomplished by monitoring the voltage at the TS pin. This system is intended to use negative temperature coefficient thermistors (NTC), which are typically integrated into the battery package. Most of the commonly used NTC thermistors in battery packs are approximately 10k at room temperature (25°C). The TS pin has been specifically designed to source 80μA of current to the thermistor. The voltage on the TS pin that results from the resistive load should stay within a window from 330mV to 2.3V. If the battery becomes too hot during charging due to an internal fault, the thermis- tor will heat up and reduce in value, pulling the TS pin voltage lower than the TS1 threshold, and the AAT2550 will signal the fault condition.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications If the use of the TS pin function is not required by the system, it should be terminated to ground with a 10k  resistor. Battery Charge Status Indication The AAT2550 indicates the status of the battery under charge with two different systems. First, the device has two status LED driver outputs. These two LEDs can indi- cate simple functions such as no battery charge activity, battery charging, charge complete, and charge fault. The AAT2550 also provides a bi-directional data reporting function so that a system microcontroller can interrogate the DATA pin and read any one of 13 system states. Status Indicator Display Simple system charging status states can be displayed using one or two LEDs in conjunction with the STAT1 and STAT2 pins on the AAT2550. These two pins are simple switches to connect the LED cathodes to ground. It is not necessary to use both display LEDs if a user simply wants to have a single lamp to show “charging” or “not charging.” This can be accomplished by using the STAT1 pin and a single LED. Using two LEDs and both STAT pins simply gives the user more information to the charging states. Refer to Table 3 for LED display definitions. The LED anodes should be connected to ADP. The LEDs should be biased with as little current as necessary to create reasonable illumination; therefore, a ballast resis- tor should be placed between the LED cathodes and the STAT1/2 pins. LED current consumption will add to the overall thermal power budget for the device package, so it is wise to keep the LED drive current to a minimum. 2mA should be sufficient to drive most low-cost green or red LEDs. It is not recommended to exceed 8mA for driv- ing an individual status LED. The required ballast resistor value can be estimated using the following formulas: For connection to the adapter supply: RB(STAT1/2) = VADP - VF(LED) ILED(STAT1/2) Example: RB(STAT1) = = 1.75k Ω5.5V - 2.0V 2mA Note: Red LED forward voltage (V F) is typically 2.0V @ 2mA. Green LED forward voltage (VF) is typically 3.2V @ 2mA. The four status LED display conditions are described in Table 3. Event Description STAT1 STAT2 Charge Disabled or Low Supply Off Off Charge Enabled Without Battery Flash 1 Flash1 Battery Charging On Off Charge Completed Off On Fault On On Table 3: Status LED Display Conditions. Digital Charge Status Reporting The AAT2550 has a comprehensive digital data reporting system by use of the DATA pin feature. This function can provide detailed information regarding the status of the charging system. The DATA pin is a bi-directional port which will read back a series of data pulses when the system microcontroller asserts a request pulse. This sin- gle strobe request protocol will invoke one of 13 possible return pulse counts which the microcontroller can look up based on the serial report table shown in Table 4. Number DATA Report Status

1 Chip Over-Temperature Shutdown

2 Battery Temperature Fault

3 Over-Voltage Turn Off

4 Not Used

5 ADP Watchdog Time-Out in

6 ADP Battery Condition Mode

7 ADP Watchdog Time-Out in

8 ADP Thermal Loop Regulation in

9 ADP Constant Current Mode

10 ADP Watchdog Time-Out in

11 ADP Constant Voltage Mode

12 ADP End of Charging

23 Data Report Error

Table 4: Serial Data Report Table. 1. Flashing rate depends on output capacitance.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications The DATA pin function is active low and should normally be pulled high to V ADP. This data line may also be pulled high to the same level as the high state for the logic I/O port on the system microcontroller. In order for the DATA pin control circuit to generate clean, sharp edges for the data output and to maintain the integrity of the data tim- ing for the system, the pull-up resistor on the data line should be low enough in value so that the DATA signal returns to the high state without delay. If too small a pull-up resistor is used, the strobe pulse from the system microcontroller could exceed the maximum pulse time and the DATA output control could issue false status reports. A 1.5k  resistor is recommended when pulling the DATA pin high to 5.0V. If the data line is pulled high to a voltage level less than 5.0V, the pull-up resistor can be calculated based on a recommended minimum pull-up current of 3mA. Use the following formula: RPULL-UP ≤ VPULL-UP 3mA Data Timing The system microcontroller should assert an active low data request pulse for minimum duration of 200ns; this is specified by the S QPULSE. Upon sensing the rising edge of the end of the data request pulse, the AAT2550 status data control will reply the data word back to the system micro- controller after a delay defined by the data report time specification T DATA(RPT). The period of the following group of data pulses will be defined by the TDATA specification. IN OUT AAT2550 Status Control DATA Pin μP GPIO Port OUT IN GPIO RPULL_UP 1.8V to 5.0V Figure 3: Data Pin Application Circuit. Timing Diagram SQ SQPULSE Data System Reset System Start CK TSYNC TLAT N=1 N=2 N=3 TOFF TDATA(RPT) = TSYNC + TLAT < 2.5 PDATA TOFF > 2 PDATA PDATA

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Capacitor Selection Input Capacitor In general, it is good design practice to place a decou- pling capacitor between the ADP pin and ground. An input capacitor in the range of 1 μF to 22 μF is recom- mended. If the source supply is unregulated, it may be necessary to increase the capacitance to keep the input voltage above the under-voltage lockout threshold during device enable and when battery charging is initiated. If the AAT2550 adapter input is to be used in a system with an external power supply source, such as a typical AC-to-DC wall adapter, then a C IN capacitor in the range of 10μF should be used. A larger input capacitor in this application will minimize switching or power bounce effects when the power supply is “hot plugged.” Output Capacitor The AAT2550 only requires a 1 μF ceramic capacitor on the BAT pin to maintain circuit stability. This value should be increased to 10μF or more if the battery connection is made any distance from the charger output. If the AAT2550 is to be used in applications where the battery can be removed from the charger, such as in the case of desktop charging cradles, an output capacitor greater than 10μF may be required to prevent the device from cycling on and off when no battery is present. Step-Down Converter Functional Description The AAT2550 has two step-down converters and both are designed with the goal of minimizing external com- ponent size and optimizing efficiency over the complete load range (600mA). Apart from the small bypass input capacitor, only a small L-C filter is required at the output. Typically, a 4.7μH inductor and a 4.7μF ceramic capacitor are recommended (see Table 5). Confi guration Output Voltage Inductor 0.6V Adjustable With External Feedback 1V, 1.2V 2.2 μH 1.5V, 1.8V 4.7 μH 2.5V, 3.3V 6.8 μH Table 5: Inductor Values. The two step-down converters can be programmed with external feedback to any voltage, ranging from 0.6V to the input voltage. An additional feed-forward capacitor can also be added to the external feedback with a 10 μF output capacitor for improved transient response (see C10 and C11 in Figure 4). At dropout, the converter duty cycle increases to 100% and the output voltage tracks the input voltage minus the R DS(ON) drop of the P-channel high-side MOSFET. The input voltage range is 2.7V to 5.5V. The converter efficiency has been optimized for all load conditions, ranging from no load to 600mA. The internal error amplifier and compensation provides excellent transient response, load, and line regulation. Soft start eliminates any output voltage overshoot when the enable or the input voltage is applied. Control Loop Both step-down converters are peak current mode control converters. The current through the P-channel MOSFET (high side) is sensed for current loop control, as well as short-circuit and overload protection. A fixed slope com- pensation signal is added to the sensed current to main- tain stability for duty cycles greater than 50%. The peak current mode loop appears as a voltage-programmed cur- rent source in parallel with the output capacitor. The output of the voltage error amplifier programs the current mode loop for the necessary peak switch current to force a constant output voltage for all load and line conditions. Internal loop compensation terminates the transconductance voltage error amplifier output. The error amplifier reference is fixed at 0.6V. Soft Start / Enable Soft start limits the current surge seen at the input and eliminates output voltage overshoot. When pulled low, the enable input forces the AAT2550 into a low-power, non-switching state. The total input current during shut- down is less than 1μA. Current Limit and Over-Temperature Protection For overload conditions, the peak input current is limit- ed. To minimize power dissipation and stresses under current limit and short-circuit conditions, switching is terminated after entering current limit for a series of pulses. Switching is terminated for seven consecutive clock cycles after a current limit has been sensed for a series of four consecutive clock cycles.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Thermal protection completely disables switching when internal dissipation becomes excessive. The junction over-temperature threshold is 140°C with 15°C of hys- teresis. Once an over-temperature or over-current fault conditions is removed, the output voltage automatically recovers. Under-Voltage Lockout Internal bias of all circuits is controlled via the VIN input. Under-voltage lockout (UVLO) guarantees sufficient V IN bias and proper operation of all internal circuitry prior to activation. Step-Down Converter Applications Information Inductor Selection The step-down converter uses peak current mode con- trol with slope compensation to maintain stability for duty cycles greater than 50%. The output inductor value must be selected so the inductor current down slope meets the internal slope compensation requirements. The internal slope compensation for the AAT2550 is 0.24A/μs. This equates to a slope compensation that is 75% of the inductor current down slope for a 1.5V out- put and 4.7μH inductor. 0.75 ⋅ VO m = = = 0.24 L 0.75 ⋅ 1.5V 4.7μH A μsec This is the internal slope compensation for the step- down converter. When externally programming the 0.6V version to 2.5V, the calculated inductance is 7.5μH. 0.75 ⋅ VO L = = ≈ 3 ⋅ VO = 3 ⋅ 2.5V = 7.5μH m 0.75 ⋅ VO 0.24A μsec A μsec A A μsec In this case, a standard 6.8μH value is selected. For high-voltage output (≥2.5V), m = 0.48A/μs. Table 5 displays inductor values for the AAT2550 step-down con- verters. Manufacturer's specifications list both the inductor DC current rating, which is a thermal limitation, and the peak current rating, which is determined by the satura- tion characteristics. The inductor should not show any appreciable saturation under normal load conditions. Some inductors may meet the peak and average current ratings yet result in excessive losses due to a high DCR. Always consider the losses associated with the DCR and its effect on the total converter efficiency when selecting an inductor. The Sumida 4.7 μH CDRH2D14 series inductor has a 135m DCR and a 1A DC current rating. At full load, the inductor DC loss is 48.6mW, which gives a 4% loss in efficiency for a 600mA, 1.5V output. Input Capacitor Select a 4.7μF to 10μF X7R or X5R ceramic capacitor for the input. To estimate the required input capacitor size, determine the acceptable input ripple level (V PP) and solve for C. The calculated value varies with input volt- age and is a maximum when V IN is double the output voltage. VO VIN CIN = VO VIN VPP IO VO VIN VO VIN CIN(MIN) = 1 VPP IO Always examine the ceramic capacitor DC voltage coeffi- cient characteristics when selecting the proper value. For example, the capacitance of a 10 μF, 6.3V, X5R ceramic capacitor with 5.0V DC applied is actually about 6 μF. The maximum input capacitor RMS current is: VO VIN VO VIN The input capacitor RMS ripple current varies with the input and output voltage and will always be less than or equal to half of the total DC load current. VO VIN VO VIN

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications for VIN = 2 · VO IO RMS(MAX)I 2= The term VO VIN VO VIN appears in both the input voltage ripple and input capacitor RMS current equations and is a maximum when V O is twice V IN. This is why the input voltage ripple and the input capacitor RMS current ripple are a maximum at 50% duty cycle. The input capacitor provides a low impedance loop for the edges of pulsed current drawn by the AAT2550. Low ESR/ESL X7R and X5R ceramic capacitors are ideal for this function. To minimize stray inductance, the capacitor should be placed as closely as possible to the IC. This keeps the high frequency content of the input current localized, minimizing EMI and input voltage ripple. Proper placement of the input capacitors (C4 and C5) can be seen in the evaluation board schematic in Figure 4. A laboratory test set-up typically consists of two long wires running from the bench power supply to the evalu- ation board input voltage pins. The inductance of these wires, along with the low-ESR ceramic input capacitor, can create a high Q network that may affect converter performance. This problem often becomes apparent in the form of excessive ringing in the output voltage dur- ing load transients. Errors in the loop phase and gain measurements can also result. Since the inductance of a short PCB trace feeding the input voltage is significantly lower than the power leads from the bench power supply, most applications do not exhibit this problem. In applications where the input power source lead induc- tance cannot be reduced to a level that does not affect the converter performance, a high ESR tantalum or alu- minum electrolytic input capacitor should be placed in parallel with the low ESR bypass ceramic input capacitor (C6 of Figure 4). This dampens the high Q network and stabilizes the system. Output Capacitor The output capacitor limits the output ripple and pro- vides holdup during large load transitions. A 4.7 μF to 10μF X5R or X7R ceramic capacitor typically provides sufficient bulk capacitance to stabilize the output during large load transitions and has the ESR and ESL charac- teristics necessary for low output ripple. The output voltage droop due to a load transient is dominated by the capacitance of the ceramic output capacitor. During a step increase in load current, the ceramic output capacitor alone supplies the load current until the loop responds. Within two or three switching cycles, the loop responds and the inductor current increases to match the load current demand. The rela- tionship of the output voltage droop during the three switching cycles to the output capacitance can be esti- mated by: COUT = 3 · ΔILOAD VDROOP · FS Once the average inductor current increases to the DC load level, the output voltage recovers. The above equa- tion establishes a limit on the minimum value for the output capacitor with respect to load transients. The internal voltage loop compensation also limits the minimum output capacitor value to 4.7μF. This is due to its effect on the loop crossover frequency (bandwidth), phase margin, and gain margin. Increased output capac- itance will reduce the crossover frequency with greater phase margin. The maximum output capacitor RMS ripple current is given by: VOUT · (VIN(MAX) - VOUT) RMS(MAX)I L · FS · VIN(MAX) Dissipation due to the RMS current in the ceramic output capacitor ESR is typically minimal, resulting in less than a few degrees rise in hot-spot temperature. Feedback Resistor Selection Table 6 shows all output voltages, which can be exter- nally programmed. Resistors R7 through R10 of Figure 4 program the output to regulate at a voltage higher than 0.6V. To limit the bias current required for the external feedback resistor string while maintaining good noise immunity, the minimum suggested value for R7 and R9 is 59k. Although a larger value will further reduce qui- escent current, it will also increase the impedance of the feedback node, making it more sensitive to external noise and interference. Table 6 summarizes the resistor values for various output voltages with R7 and R9 set to either 59k  for good noise immunity or 221k  for reduced no load input current.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications VOUT (V) R7, R9 = 59k R8, R10 (k) R7, R9 = 221k R8, R10 (k) 0.8 19.6 75 0.9 29.4 113 1.0 39.2 150 1.1 49.9 187 1.2 59.0 221 1.3 68.1 261 1.4 78.7 301 1.5 88.7 332 1.8 118 442 1.85 124 464 2.0 137 523 2.5 187 715 3.3 267 1000 Table 6: Adjustable Resistor Values for Use With 0.6V Step-Down Converter. The AAT2550, combined with an external feedforward capacitor (C10 and C11 in Figure 4), delivers enhanced transient response for extreme pulsed load applications. The addition of the feedforward capacitor (100pF) typi- cally requires a larger output capacitor for stability. VOUT VREF 1.5V 0.6V Thermal Considerations The AAT2550 is available in a 4x4mm QFN package, which has a typical thermal resistance of 50°C/W when the exposed paddle is soldered to a printed circuit board (PCB) in the manner discussed in the Printed Circuit Board Layout section of this datasheet. Thermal resis- tance will vary with the PCB area, ground plane area, size and number of other adjacent components, and the heat they generate. The maximum ambient operating temperature is limited by either the design derating cri- teria, the over-temperature shutdown temperature, or the thermal loop charge current reduction control. To calculate the junction temperature, sum the step-down converter losses with the battery charger losses. Multiply the total losses by the package thermal resistance and add to the ambient temperature to determine the junc- tion temperature rise. TJ(MAX) = (PSD + PC) · θJA + TAMB PSD is the total loss associated with both step-down con- verters and P C is the loss associated with the charger. The total losses will vary considerably depending on input voltage, load, and charging current. While charg- ing a battery, the current capability of the step-down converters is limited. Step-Down Converter Losses There are three types of losses are associated with the AAT2550 step-down converter: switching losses (t SW · FS), conduction losses (I2 · R DS(ON)), and quiescent cur- rent losses (I Q · V IN). At full load, assuming continuous conduction mode, a simplified form of the step-down converter losses is: PSD = + (tSW · FS · (IOA + IOB) + 2 · IQ ) · VIN IOA 2 · (RDS(ON)H · VOA + RDS(ON)L · (VIN - VOA)) + IOB 2 · (RDS(ON)H · VOB + RDS(ON)L · (VIN - VOB)) VIN For the condition where one channel is in dropout at 100% duty cycle (IOA), the step-down converter dissipa- tion is: PSD = IOA 2 · RDS(ON)H + (tSW · FS · IOB + 2 · IQ ) · VIN + IOB 2 · (RDS(ON)H · VOB + RDS(ON)L · (VIN - VOB)) VIN PSD = Step-Down Converter Dissipation VIN = Converter Input Voltage RDS(ON)H = High Side MOSFET On Resistance RDS(ON)L = Low Side MOSFET On Resistance VOA = Converter A Output Voltage VOB = Converter B Output Voltage IOA = Converter A Load Current IOB = Converter B Load Current IQ = Converter Quiescent Current tSW = Switching Time Estimate FS = Converter Switching Frequency Always use the R DS(ON) and quiescent current value that corresponds to the applied input voltage.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Battery Charger Losses The maximum battery charger loss is: PC = (VADP - VMIN) · ICH + VADP · IQC PC = Total Charger Dissipation VADP = Adapter Voltage VMIN = Preconditioning Voltage Threshold ICH = Programmed Charge Current IQC = Charger Quiescent Current Consumed by the Charger For an application where no load is applied to the step- down converters and the charger current is set to 1A with V ADP = 5.0V, the maximum charger dissipation occurs at the preconditioning voltage threshold V MIN. PC = (VADP - VMIN) · ICH + VADP · IQC = 2W The charger thermal loop begins reducing the charge current at a 110°C junction temperature (T LOOP_IN). The ambient temperature at which the charger thermal loop begins reducing the charge current is: TA = TLOOP_IN - θJA · PC = 10°C Therefore, under the given conditions, the AAT2550 bat- tery charger will enter the thermal loop charge current reduction at an ambient temperature greater than 10°C. Total Power Loss Examples The most likely high power scenario is when the charger and step-down converter are both operational and pow- ered from the adapter. To examine the step-down con- verter maximum current capability for this condition, it is necessary to determine the step-down converter MOSFET R DS(ON), quiescent current, and switching losses at the adapter voltage level (5V). This example shows that with a 600mA battery charge current, the buck converter out- put current capability is limited 400mA. This limits the junction temperature to 110°C and avoids the thermal loop charge reduction at a 70°C ambient temperature. Conditions: VOA 2.5V @ 400mA Step-Down Converter A VOB 1.8V @ 400mA Step-Down Converter B IQ 70μA Converter Quiescent Current VIN = VADP 5.0V Charger and Step-Down VMIN 3.0V Battery Preconditioning Threshold Voltage ICH 0.6A Battery Charge Current IOP 0.75mA Charger Operating Current The step-down converter load current capability is great- est when the battery charger is disabled. The following example demonstrates the junction temperature rise for conditions where the battery charger is disabled and full load is applied to both converter outputs at the nominal battery input voltage. PTOTAL = + (tSW · FS · (IOA + IOB) + 2 · IQ) · VIN + (VADP - VMIN) · ICH + VADP · IOP IOA 2 · (RDS(ON)H · VOA + RDS(ON)L · (VIN - VOA)) + IOB 2 · (RDS(ON)H · VOB + RDS(ON)L · (VIN - VOB)) VIN 5.0V TJ(MAX) = TAMB + (θJA · PLOSS) = 139°C Conditions: VOA 2.5V @ 600mA Step-Down Converter A VOB 1.8V @ 600mA Step-Down Converter B IQ 70μA Converter Quiescent Current VIN 3.6V Charger and Step-Down Con- verter Input Voltage ICH = IOP 0A Charger Disabled PTOTAL = + (tSW · FS · (IOA + IOB) + 2 · IQ) · VIN + (VADP - VMIN) · ICH + VADP · IOP IOA 2 · (RDS(ON)H · VOA + RDS(ON)L · (VIN - VOA)) + IOB 2 · (RDS(ON)H · VOB + RDS(ON)L · (VIN - VOB)) VIN 3.6V TJ(MAX) = TAMB + (θJA · PLOSS) = 107.15°C

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Printed Circuit Board Layout Use the following guidelines to ensure a proper printed circuit board layout. 1. Step-down converter bypass capacitors (C4 and C5 in Figure 4) must be placed as close as possible to the step-down converter inputs. 2. The connections from the LXA and LXB pins of the step-down converters to the output inductors should be kept as short as possible. This is a switching node, so minimizing the length will reduce the potential of this noisy trace interfering with other high impedance noise sensitive nodes. 3. The feedback trace should be separate from any power trace and connected as closely as possible to the load point. Sensing along a high current load trace will degrade the DC load regulation. If external feedback resistors are used, they should be placed as closely as possible to the FB pins and AGND. This prevents noise from being coupled into the high impedance feedback node. 4. The resistance of the trace from the load return to GND should be kept to a minimum. This minimizes any error in DC regulation due to differences in the potential of the internal signal ground and the power ground. 5. For good thermal coupling, vias are required from the pad for the QFN paddle to the ground plane. Via diameters should be 0.3mm to 0.33mm and posi- tioned on a 1.2mm grid. Avoid close placement to other heat generating devices. 6. Minimize the trace impedance from the battery to the BAT pin. The charger output is not remotely sensed, so any drop in the output across the BAT output trace feeding the battery will add to the error in the EOC battery voltage. To minimize voltage drops on the PCB, maintain an adequate high current carrying trace width.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications EnVoA Adapter GND Data Strobe SW1 STAT1 STAT2 4.7μHL2 6.8μHL1 ENA LXA PGND DATA4 N/C5 ADPSET6 N/C BA AD AGND AGND ENBA TS 13 STAT2 14 STAT1 15 CT 16 PGND 17 LXB 18 ENB VINB FBB AGND FBA VINA AAT2550 U14.7μF C8 4.7μF 10μF 10μF Charger Enable Battery ADP BAT GND TS 10μF 0.1μF C12 118k R10 59k 59k 187k (opt) 100pF C11 (opt.) 100pF C10 1.5k 1.5k 8.06k VIN VoB VoA CT GND GND GND EnVoB(opt) 120μF 1kR3 (open) C14 Data LXA LXB VoA, VoB (V) R8, R10 ( Ω) 1.0 1.2 1.5 1.8 2.5 3.0 3.3 9.2k 59k 88.7k 118k 187k 237k 267k 2.2μH (CDRH2D14; DCR 75mΩ; 1200mA @ 20°C) 2.2μH (CDRH2D14; DCR 75mΩ; 1200mA @ 20°C) 4.7μH (CDRH2D14; DCR 135mΩ; 1000mA @ 20°C) 4.7μH (CDRH2D14; DCR 135mΩ; 1000mA @ 20°C) 6.8μH (CDRH2D14; DCR 170mΩ; 850mA @ 20°C) 6.8μH (CDRH2D14; DCR 170mΩ; 850mA @ 20°C) 6.8μH (CDRH2D14; DCR 170mΩ; 850mA @ 20°C) L1, L2 VoA VoB 10k Green Red 10μF C13 Figure 4: AAT2550 Evaluation Board Schematic.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Qty. Description Reference Designator Manufacturer Part Number 1 Conn. Term Block 2.54mm 2 POS Adapter Input Phoenix Contact 1 Conn. Term Block 2.54mm 3 POS Battery Output Phoenix Contact

3 Ceramic Capacitor 10 μF 10%, 10V, X5R, 0805 C3, C4, C5, C13 Murata

2 Ceramic Capacitor 4.7 μF 10%, 6.3V, X5R, 0805 C8,C9 Murata 1 Ceramic Capacitor 0.1 μF 25V 10% X5R 0603 C12 Vishay 1 Tantalum Capacitor 100 μF, 6.3V, Case C C6 Vishay

2 Optional Ceramic Capacitor 100pF, 0402, COG C10, C11 Vishay

2 Ferrite Shielded Inductor CDRH2D14 L1, L2 Sumida

2 1.5k, 5%, 1/16W, 0402 R1,R2 Vishay 1 1.0k, 5%, 1/16W, 0402 R3 Vishay 1 8.06k, 1%, 1/16W, 0402 R6 Vishay 2 59.0k, 1%, 1/16W, 0402 R7,R9 Vishay 1 118k, 1%, 1/16W, 0402 R10 Vishay 1 187k, 1%, 1/16W, 0402 R8 Vishay 1 10k, 5%, 1/16W, 0402 R4 Vishay

1 Red LED, 1206 D1 Chicago Miniature Lamp CMD15-21SRC/TR8

1 Green LED, 1206 D2 Chicago Miniature Lamp CMD15-21SRC/TR8

1 Switch Tact 6mm SPST H = 5.0mm SW1 ITT Industries/C&K Div CKN9012-ND

1 AAT2550 Total Power Solution for Portable

Table 7: AAT2550 Evaluation Board Bill of Materials. Manufacturer Part Number Inductance (μH) Max DC Current (A) DCR () Size (mm) LxWxH Type Table 8: Typical Surface Mount Inductors. Manufacturer Part Number Value Voltage Temp. Co. Case Murata GRM219R61A475KE19 4.7 μF 10V X5R 0805 Murata GRM21BR60J106KE19 10 μF 6.3V X5R 0805 Murata GRM21BR60J226ME39 22 μF 6.3V X5R 0805 Table 9: Surface Mount Capacitors.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Adjustable Version (0.6V device) VOUT (V) R7, R9 = 59k R8, R10 (k) R7, R9 = 221k1 R8, R10 (k) L1, L2 (μH) 0.8 19.6 75.0 2.2 0.9 29.4 113 2.2 1.0 39.2 150 2.2 1.1 49.9 187 2.2 1.2 59.0 221 2.2 1.3 68.1 261 2.2 1.4 78.7 301 4.7 1.5 88.7 332 4.7 1.8 118 442 4.7 1.85 124 464 4.7 2.0 137 523 6.8 2.5 187 715 6.8 3.3 267 1000 6.8 Table 10: Evaluation Board Component Values. 1. For reduced quiescent current, R7 and R9 = 221k .

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Step-Down Converter Design Example Specifications VOA = 2.5V @ 400mA (VFBA = 0.6V), pulsed load ILOAD = 300mA VOB = 1.8V @ 400mA (VFBB = 0.6V), pulsed load ILOAD = 300mA VIN = 2.7V to 4.2V (3.6V nominal) FS = 1.4MHz TAMB = 85°C 2.5V VOA Output Inductor L1 = 3 ⋅ VO1 = 3 ⋅ 2.5V = 7.5μHμsec A μsec A (see Table 5) For Sumida inductor CDRH2D14, 6.8μH, DCR = 170m. IPKA = IOA + ΔIA = 0.4A + 0.053A = 0.453A2 PLA = IOA 2 ⋅ DCR = 0.452 ⋅ 170mΩ = 34mW 1.8V VOB Output Inductor L2 = 3 ⋅ VO2 = 3 ⋅ 1.8V = 5.4μHμsec A μsec A (see Table 5) For Sumida inductor CDRH2D14, 4.7μH, DCR = 135m. IPKB = IOB + ΔIB = 0.4A + 0.078A = 0.48A2 PLB = IOB 2 ⋅ DCR = 0.4A2 ⋅ 135mΩ = 21.6mW

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications 2.5V Output Capacitor 10μH · 1.4MHz · 4.2V 23 RMS(MAX)I L · FS · VIN(MAX) 3 · ΔILOAD VDROOP · FS 3 · 0.3A 0.2V · 1.4MHz COUT = = = 3.2 μF

• = 21mArms (VOUT) · (VIN(MAX) - VOUT) = Pesr = esr · IRMS 2 = 5mΩ · (21mA)2 = 2.2μW 1.8V Output Capacitor 4.7μH · 1.4MHz · 4.2V 23 RMS(MAX)I L · FS · VIN(MAX) 3 · ΔILOAD VDROOP · FS 3 · 0.3A 0.2V · 1.4MHz COUT = = = 3.2 μF
• = 45mArms (VOUT) · (VIN(MAX) - VOUT) = Pesr = esr · IRMS 2 = 5mΩ · (45mA)2 = 10μW Input Capacitor Input Ripple VPP = 25mV. CIN = = = 6.8 μF1 VPP IO1 + IO2 25mV 0.8A IO1 + IO2 RMS(MAX)I P = esr · IRMS 2= = 0.4Arms

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications

Ordering Information

Marking1 Part Number (Tape and Reel)2Package Converter 1 Converter 2 QFN44-24 0.6V 0.6V RJXYY AAT2550ISK-CAA-T1 Skyworks Green™ products are compliant with all applicable legislation and are halogen-free. For additional information, refer to Skyworks Definition of Green™ , document number SQ04-0074. Legend Voltage Code Adjustable (0.6V) A 0.9 B 1.2 E 1.5 G 1.8 I 1.9 Y 2.5 N 2.6 O 2.7 P 2.8 Q 2.85 R 2.9 S 3.0 T 3.3 W 4.2 C 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202174B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013 AAT2550 DATA SHEET Total Power Solution for Portable Applications Copyright © 2012, 2013 Skyworks Solutions, Inc. All Rights Reserved. Information in this document is provided in connection with Skyworks Solutions, Inc. (“Skyworks”) products or services. These materials, including the information contained herein, are provided by Skyworks as a service to its customers and may be used for informational purposes only by the customer. Skyworks assumes no responsibility fo r errors or omissions in these materials or the information contained herein. Sky- works may change its documentation, products, services, specifi cations or product descriptions at any time, without notice. Skyworks makes no commitment to update the materials or information and shall have no responsibility whatsoever for confl icts, incompatibilities, or other diffi culties arising from any future changes. No license, whether express, implied, by estoppel or otherwise, is granted to any intellectual property rights by this document. Skyworks assumes no liability for any materials, products or information provided here- under, including the sale, distribution, reproduction or use of Skyworks products, information or materials, except as may be provided in Skyworks Terms and Conditions of Sale. THE MATERIALS, PRODUCTS AND INFORMATION ARE PROVIDED “AS IS” WITHOUT WARRANTY OF ANY KIND, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHERWISE, INCLUDING FITNESS FOR A PARTICULAR PURPOSE OR USE, MERCHANTABILITY, PERFORMANCE, QUALITY OR NON-INFRINGEMENT OF ANY INTELLECTUAL PROPERTY RIGHT; ALL SUCH WARRANTIES ARE HEREBY EXPRESSLY DISCLAIMED. SKYWORKS DOES NOT WARRANT THE ACCURACY OR COMPLETENESS OF THE INFORMATION, TEXT, GRAPHICS OR OTHER ITEMS CONTAINED WITHIN THESE MATERIALS. SKYWORKS SHALL NOT BE LIABLE FOR ANY DAMAGES, IN- CLUDING BUT NOT LIMITED TO ANY SPECIAL, INDIRECT, INCIDENTAL, STATUTORY, OR CONSEQUENTIAL DAMAGES, INCLUDING WITHOUT LIMITATION, LOST REVENUES OR LOST PROFITS THAT MAY RESULT FROM THE USE OF THE MATERIALS OR INFORMATION, WHETHER OR NOT THE RECIPIENT OF MATERIALS HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. Skyworks products are not intended for use in medical, lifesaving or life-sustaining applications, or other equipment in which the failure of the Skyworks products could lead to personal injury, death, physical or en- vironmental damage. Skyworks customers using or selling Skyworks products for use in such applications do so at their own risk and agree to fully indemnify Skyworks for any damages resulting from such improper use or sale. Customers are responsible for their products and applications using Skyworks products, which may deviate from published specifi cations as a result of design defects, errors, or operation of products outside of pub- lished parameters or design specifi cations. Customers should include design and operating safeguards to minimize these and other risks. Skyworks assumes no liability for applications assistance, customer product design, or damage to any equipment resulting from the use of Skyworks products outside of stated published specifi cations or parameters. Skyworks, the Skyworks symbol, and “Breakthrough Simplicity” are trademarks or registered trademarks of Skyworks Solutions, Inc., in the United States and other countries. Third-party brands and names are for identifi cation purposes only, and are the property of their respective owners. Additional information, including relevant terms and conditions, posted at www.skyworksinc.com, are incorporated by reference.

Package Information

4.000 ± 0.050 2.7 ± 0.05 0.300 × 45° Pin 1 Dot By Marking 4.000 ± 0.050 2.7 ± 0.05 0.5 BSC 0.4 ± 0.05 0.305 ± 0.075 0.900 ± 0.050 0.025 ± 0.025 0.214 ± 0.036 Pin 1 Identification R0.030Max 712 19 24 Top View Bottom View Side View All dimensions in millimeters. 1. The leadless package family, which includes QFN, TQFN, DFN, TDFN and STDFN, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder c onnection.