AAT1142 SKYWORKS | Alldatasheet

Document overview

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  • PDF pages: 20

Technical content

Features

  • V IN Range: 2.7V to 5.5V
  • V OUT Programmable Range: 0.6V to 2.0V
  • Dynamic Voltage Management: ▪ 50mV Output Resolution ▪ Fast, Stable Response
  • Serial Control Options: ▪ I 2C Two-Wire Interface ▪ S 2Cwire Single-Wire Interface
  • 800mA Output Current
  • Up to 93% Efficiency
  • Line, Load Regulation Less Than ±0.5%
  • 2.2MHz Switching Frequency
  • Ultra-Small External Filter
  • Low 35 μA No Load Quiescent Current
  • 100% Duty Cycle Low Dropout Operation
  • Internal Soft Start
  • Over-Temperature Protection
  • Current Limit Protection
  • Multi-Function MODE/SYNC Pin: ▪ PFM/PWM for High Efficiency ▪ PWM Only for Low Noise ▪ Clock Input to Synchronize to System Clock
  • TDFN33-12 Package
  • Temperature Range: -40°C to +85°C

Applications

  • Camcorders
  • Cellular Phones and Smartphones
  • Digital Still Cameras
  • Handheld Instruments
  • Microprocessor / DSP Core
  • MP3, Portable Music, and Portable Media Players
  • PDAs and Handheld Computers Typical Application LXPVIN, VIN AAT1142 MODE/SYNC PGND FB 2.2μH AGND 4.7μF 10μF VIN: 2.7V to 5.5V VOUT: 0.6V to 2.0V 800mA Maximum SDA SCL EN/SET I2C S2Cwire* *Optional S2Cwire or I2C Input Efficiency vs. Load (VOUT = 1.8V) Output Current (mA) Efficiency (%) 100 0 1 10 100 1000 PWM Only Mode VIN = 2.7VVIN = 3.6V VIN = 4.2V VIN = 5.0V

800mA Voltage-Scaling Step-Down Converter Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012 Pin Descriptions Pin Number Symbol Function 12 LX Connect the output inductor to this pin. The switching node is internally connected to the drain of both high- and low-side MOSFETs. 11 PGND Main power ground return pin. Connect to the output and input capacitor return.

10 MODE/SYNC

Connect to ground for PFM/PWM mode and optimized effi ciency throughout the load range. Connect to high for low noise PWM Only operation under all operating condi- tions. Connect to an external clock for synchronization (PWM Only).

9 SDA I

2C control pin: Data input. 8 SCL I 2C control pin: Clock input. 7 EN/SET I2C enable pin. Pull high to enable the AAT1142; pull low to disable the AAT1142. Also serves as S2Cwire input for programmable output voltages. 6F B Feedback input pin. This pin is connected directly to the converter output for pro- grammable output. 4, 5 AGND Ground connection pin. 3 VIN Input voltage for the converter. 1 PVIN Input voltage for the power switches. 2 N/C Not connected. EP Exposed paddle (bottom); connect to ground as closely as possible to the device. Pin Configuration TDFN33-12 (Top View) PVIN N/C VIN AGND AGND FB LX PGND MODE/SYNC SDA SCL EN/SET

800mA Voltage-Scaling Step-Down Converter Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012 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 board. 3. Derate 20mW/°C above 25°C. Absolute Maximum Ratings1 Symbol Description Value Units VIN, PVIN Input Voltage and Input Power to GND 6.0 V VLX LX to GND -0.3 to VIN + 0.3 VFB FB to GND -0.3 to VIN + 0.3 VSDA/SCL SDA/SCL to GND -0.3 to 6.0 VMODE/SYNC, VEN/SET MODE/SYNC and EN/SET to GND -0.3 to 6.0 TJ Operating Junction Temperature Range -40 to 150 °CTLEAD Maximum Soldering Temperature (at leads, 10 sec) 300 Thermal Information2 Symbol Description Value Units PD Maximum Power Dissipation 3 2.0 W JA Thermal Resistance 50 °C/W

800mA Voltage-Scaling Step-Down Converter Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012 1. The AAT1142 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. Electrical Characteristics1 L = 2.2 μH, CIN = C OUT = 10 μF, 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 Converter VIN Input Voltage 2.7 5.5 V VUVLO UVLO Threshold VIN Rising 2.7 Hysteresis 250 mV V IN Falling 2.0 V VOUT Output Voltage Tolerance I OUT = 0mA to 800mA, VIN = 2.7V to 5.5V -3.0 3.0 % VOUT VOUT Programmable Range 0.6 2.0 V VSLEW Output Voltage Programming Slew Rate C OUT = 10μF 10 mV/ μs IQ Quiescent Current No Load 35 70 μAISHDN Shutdown Current EN/SET = AGND = PGND 1.0 ILIM P-Channel Current Limit 1.0 A RDS(ON)H High Side Switch On Resistance 0.29 RDS(ON)L Low Side Switch On Resistance 0.24 ILXLEAK LX Leakage Current V IN = 5.5V, VLX = 0V to VIN 1 μA VOUT/ VOUT*VIN Line Regulation V IN = 2.7V to 5.5V 0.2 %/V ROUT Output Impedance 250 k  TS Start-Up Time From Enable to Output Regulation 100 μs FOSC Oscillator Frequency 2.2 MHzFSYNC SYNC Frequency Range 1.0 3.0 TSD Over-Temperature Shutdown Threshold 140 °CTHYS Over-Temperature Shutdown Hysteresis 15 EN/SET and MODE/SYNC VEN/SET(L) Enable Threshold Low 0.6 VVEN/SET(H) Enable Threshold High 1.4 TEN/SET(L) EN/SET Low Time V EN/SET < 0.6V 0.3 75 μsTEN/SET(H) EN/SET High Time V EN/SET > 1.4V 50 75 TOFF EN/SET Timeout V EN/SET < 0.6V 500 TLATCH EN/SET Latch Timeout V EN/SET > 1.4V 500 IEN/SET Input Low Current V IN = VFB = 5.5V -1.0 1.0 μA VMODE/SYNC(L) Enable Threshold Low VIN · 0.4 V VMODE/SYNC(H) Enable Threshold High VIN · 0.7 IMODE/SYNC Input Low Current -1.0 1.0 μA

800mA Voltage-Scaling Step-Down Converter Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012 Characteristics of SDA and SCL Bus Lines Parameter Symbol Standard Mode Fast Mode UnitsMin Max Min Max SCL Clock Frequency Hold Time for START Condition; After this Period, the First Clock Pulse is Generated fSCL 100 400 kHz tHD;STA 4.0 0.6 μs LOW Period of the SCL Clock t LOW 4.7 1.3 HIGH Period of the SCL Clock t HIGH 4.0 0.6 Set-up Time for a Repeated START Condition t SU;STA 4.7 0.6 Data in Hold Time t HD;DAT 0 3.45 0 0.9 Data in Set-Up Time t SU;DAT 350 350 μsSet-Up Time for STOP Condition t SU;STO 4.0 0.6 Bus Free Time Between a STOP and START Condition t BUF 4.7 1.3 μs Input Low Level V IL VIN· 0.3 V IN · 0.3 VInput High Level V IH VIN · 0.7 V IN · 0.7

800mA Voltage-Scaling Step-Down Converter Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012 Typical Characteristics Efficiency vs. Load (VOUT = 0.9V) Output Current (mA) Efficiency (%) 100 0 1 10 100 1000 VIN = 2.7VVIN = 3.6V VIN = 4.2V VIN = 5.0V PWM Only Mode DC Regulation (VOUT = 0.9V) Output Current (mA) Output Accuracy (%) -2.0 -1.0 0.0 1.0 2.0 0 1 10 100 1000 VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5.0V Efficiency vs. Load (VOUT = 1.0V) Output Current (mA) Efficiency (%) 100 0 1 10 100 100 VIN = 2.7VVIN = 3.6V VIN = 4.2V VIN = 5.0V PWM Only Mode DC Regulation (VOUT = 1.0V) Output Current (mA) Output Accuracy (%) -2.0 -1.0 0.0 1.0 2.0 0 1 10 100 1000 VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5.0V Efficiency vs. Load (VOUT = 1.2V) Output Current (mA) Efficiency (%) 100 0 1 10 100 1000 VIN = 2.7VVIN = 3.6V VIN = 4.2V VIN = 5.0V PWM Only Mode DC Regulation (VOUT = 1.2V) Output Current (mA) Output Accuracy (%) -2.0 -1.0 0.0 1.0 2.0 0 1 10 100 1000 VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5.0V

800mA Voltage-Scaling Step-Down Converter Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012 Typical Characteristics Efficiency vs. Load (VOUT = 1.8V) Output Current (mA) Efficiency (%) 100 0 1 10 100 1000 PWM Only Mode VIN = 2.7VVIN = 3.6V VIN = 4.2V VIN = 5.0V DC Regulation (VOUT = 1.8V) Output Current (mA) Output Accuracy (%) -2.0 -1.6 -1.2 -0.8 -0.4 0.0 0.4 0.8 1.2 1.6 2.0 0 1 10 100 100 0 VIN = 4.2V VIN = 5.0V VIN = 3.6V VIN = 2.7V Soft Start (VIN = 3.6V; VOUT = 1.8V; IOUT = 800mA) Output and Enable Voltage (top) (V) Inductor Current (bottom) (A) -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 -0.5 0.5 1.5 2.5 3.5 Time (50μs/div) Line Regulation (VOUT = 1.0V) Input Voltage (V) Output Accuracy (%) -1.00 -0.75 -0.50 -0.25 0.00 0.25 0.50 0.75 1.00 IOUT = 650mA IOUT = 0mAIOUT = 100mA Output Voltage Accuracy vs. Temperature (VIN = 3.6V; VOUT = 1.0V; IOUT = 400mA) Temperature (°°C) Accuracy (%) -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 - 4 0 - 3 0 - 2 0 - 1 00 1 02 03 04 05 06 07 08 0 Switching Frequency vs. Temperature (VIN = 3.6V; VOUT = 1.0V; IOUT = 400mA) Temperature (°°C) Variation (%) -10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 - 4 0 - 3 0 - 2 0 - 1 00 1 02 03 04 05 06 07 08 0

800mA Voltage-Scaling Step-Down Converter Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012 Typical Characteristics P-Channel RDS(ON) vs. Input Voltage Input Voltage (V) RDS(ON)H (mΩΩ) 200 250 300 350 400 450 125°C 100°C 85°C 25°C N-Channel RDS(ON) vs. Input Voltage Input Voltage (V) RDS(ON)L (mΩΩ) 150 200 250 300 350 400 450 125°C 100°C 85°C 25°C Load Transient Response (10mA to 400mA; VIN = 3.6V; VOUT = 1.2V) Output Voltage (top) (V) Load and Inductor Current (bottom) (200mA/div) Time (50μs/div) 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 Load Transient Response (400mA to 800mA; VIN = 3.6V; VOUT = 1.0V) Output Voltage (top) (V) Load and Inductor Current (bottom) (200mA/div) Time (50μs/div) -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 No Load Quiescent Current vs. Input Voltage (VOUT = 1.8V) Input Voltage (V) Supply Current (µA) 85°C 25°C -40°C Line Response (VOUT = 1.2V; IOUT = 650mA) Output Voltage (top) (VAC) Input Voltage (bottom) (V) Time (500μs/div) -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 3.0 3.5 4.0 4.5 5.0 5.5 6.0

800mA Voltage-Scaling Step-Down Converter Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012 Typical Characteristics Output Ripple (VIN = 4.2V; VOUT = 0.8V; No Load) Output Voltage (top) (V) Inductor Current (bottom) (A) Time (4μs/div) 0.60 0.65 0.70 0.75 0.80 0.85 0.90 -0.02 0.00 0.02 0.04 0.06 0.08 0.10 Output Ripple (VIN = 4.2V; VOUT = 0.8V; IOUT = 650mA) Output Voltage (top) (V) Inductor Current (bottom) (A) Time (200ns/div) 0.72 0.73 0.74 0.75 0.76 0.77 0.78 0.79 0.80 0.81 0.82 0.60 0.62 0.64 0.66 0.68 0.70 0.72 0.74 0.76 0.78 0.80 Output Programming Step from 0.9V to 1.2V (VIN = 3.6V; ROUT = 1.85ΩΩ) Output Voltage (top) (V) Output Current (bottom) (A) Time (50μs/div) 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 1.30 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 Output Programming Step from 1.2V to 0.9V (VIN = 3.6V; ROUT = 1.85ΩΩ) Output Voltage (top) (V) Output Current (bottom) (A) Time (50μs/div) 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 1.30 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90

800mA Voltage-Scaling Step-Down Converter Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012 Functional Description The AAT1142 is a high performance, 800mA step-down converter with an input voltage range from 2.7V to 5.5V. The AAT1142 uses Dynamic Voltage Manage ment, which allows the system host to quickly set the output voltage through the integrated I 2C or S2Cwire interface. Through this interface, the host can change the output voltage to track processor idle and active states, greatly extending battery life without degrading system performance. I provides an industry-standard, dual-line interface, while S 2Cwire provides a single-line, high-speed serial inter- face. The 2.2MHz switching frequency allows the use of small external components. Only three external components are needed to program the output from 0.6V to 2.0V. Typically, one 4.7μF capacitor, one 10 μF capacitor, and one 2.2μH inductor are required. The integrated low-loss MOSFET switches provide up to 93% efficiency. PFM operation maintains high efficiency under light load conditions (typically <50mA). Pulling the MODE/SYNC pin high allows optional PWM Only low noise mode. This maintains constant frequency and low output ripple across all load conditions. Alternatively, the IC can be synchronized to an external clock via the MODE/SYNC input. External synchronization can be maintained between 1MHz and 3MHz. At low input voltages, the converter dynamically adjusts the operating frequency prior to dropout to maintain the required duty cycle and provide accurate output regula- Functional Block Diagram SCL LXLogic DH DL PGND AGND PVINVINFB SDA EN/SET MODE/SYNC Control Logic Voltage Reference Err. Amp.

800mA Voltage-Scaling Step-Down Converter Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012 tion. Output regulation is maintained until the dropout voltage, or minimum input voltage, is reached. The AAT1142 achieves better than ±0.5% output regula- tion across the input voltage and output load range. Maximum continuous load is 800mA. A current limit of 1A (typical) protects the IC and system components from short-circuit damage. Typical no load quiescent cur- rent is 35μA. Thermal protection completely disables switching when the maximum junction temperature is detected. The junction over-temperature threshold is 140°C with 15°C of hysteresis. Once an over-temperature or over-current fault condition is removed, the output voltage automati- cally recovers. Peak current mode control and optimized internal com- pensation provide high loop bandwidth and excellent response to input voltage and fast load transient events. The output voltage is stable across all operating condi- tions, ensuring fast transitions with no overshoot or ring- ing. Soft start eliminates output voltage overshoot when the enable or the input voltage is applied. Under-voltage lockout prevents spurious start-up events. Control Loop The AAT1142 is a peak current mode step-down con- verter. 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 compensa- tion signal is added to the sensed current to maintain stability for duty cycles greater than 50%. The peak cur- rent 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. Loop stability and fast transient response are maintained across the entire input and output voltage range with a small 2.2μH output inductor and 10μF output capacitor. 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 AAT1142 into a low-power, non-switching state. The total input current during shut- down is less than 1 μA. The turn-on time from EN to output regulation is 100μs (typical). Alternatively, the EN/SET pin serves as the input for S 2Cwire single line control. Details of S 2Cwire operation and timing diagrams are provided in the Applications Information section of this datasheet. Current Limit and Over-Temperature Protection Switching is terminated after entering current limit for a series of pulses to minimize power dissipation and stresses under overload and short-circuit conditions. 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 condition 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.

800mA Voltage-Scaling Step-Down Converter Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012 Data Register Data Bits Output Voltage (V)D7 D6 D5 D4 D3 D2 D1 D0 1 XX000000 0.60 2 XX000001 0.65 3 XX000010 0.70 4 XX000011 0.75 5 XX000100 0.80 6 X X 0 0 0 1 0 1 0.85 7 X X 0 0 0 1 1 0 0.90 8 XX000111 0.95 9 XX001000 1.00 1 0 X0001001 1.05 1 1 XX001010 1.10 1 2 XX001011 1.15 1 3 XX001100 1.20 (default) 14 X X 0 0 1 1 0 1 1.25 15 X X 0 0 1 1 1 0 1.30 1 6 XX001111 1.35 1 7 XX010000 1.40 1 8 XX010001 1.45 1 9 XX010010 1.50 2 0 XX010011 1.55 2 1 XX010100 1.60 22 X X 0 1 0 1 0 1 1.65 23 X X 0 1 0 1 1 0 1.70 2 4 XX010111 1.75 2 5 XX011000 1.80 2 6 XX011001 1.85 2 7 XX011010 1.90 2 8 XX011011 1.95 2 9 XX011100 2.00 3 0 XX011101 2.00 31 X X 0 1 1 1 1 0 2.00 3 2 XX011111 2.00 Table 1: AAT1142 I2C Output Voltage Programming Map (X = don’t care). S2Cwire Serial Interface Skyworks' S2Cwire serial interface is a proprietary high- speed single-wire interface. The S2Cwire interface records rising edges of the EN/SET input and decodes them into one of 32 registers which determines the output voltage, as shown in Table 2. Each state corresponds to an output voltage setting. When using the S 2Cwire interface, both I2C inputs should be tied to the ground return. This disables the I 2C func- tionality. S2Cwire Serial Interface Timing The S2Cwire serial interface has flexible timing. Data can be clocked-in at speeds up to 1MHz. After data has been submitted, EN/SET is held high to latch the data for a period T LAT. The output is subsequently changed to the predetermined voltage. When EN/SET is set low for a time greater than T OFF, the AAT1142 is disabled. When disabled, the data register is reset to the default value.

800mA Voltage-Scaling Step-Down Converter Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012 Rising Clock Edges/Data Register Output Voltage (V) Rising Clock Edges/Data Register Output Voltage (V) 1 No change 17 1.40 2 0.65 18 1.45 3 0.70 19 1.50 4 0.75 20 1.55 5 0.80 21 1.60 6 0.85 22 1.65 7 0.90 23 1.70 8 0.95 24 1.75 9 1.00 25 1.80 10 1.05 26 1.85 11 1.10 27 1.90 12 1.15 28 1.95 13 1.20 (default) 29 2.00 14 1.25 30 2.00 15 1.30 31 2.00 16 1.35 32 2.00 Table 2: AAT1142 S2Cwire Output Voltage Programming Map. Component Selection 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 programmable AAT1142 is 0.61A/μs. This equates to a slope compensa- tion that is 75% of the inductor current down slope for a 1.8V output and 2.2μH inductor. 0.75 · VO m = = = 0.61 L 0.75 · 1.8V 2.2μH A μs 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 2.2 μH CDRH2D14 series Sumida inductor has a 94m DCR and a 1.5A DC current rating. At full 800mA load, the inductor DC loss is 60mW which gives a 4.8% loss in efficiency for an 800mA, 1.0V 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 voltage 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 F, 6.3V, X5R ceramic S2Cwire Timing Diagram EN/SET 2 n-1 n ≤ 64 Data Reg 0n 0 THI TLO TLAT TOFF

800mA Voltage-Scaling Step-Down Converter Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012 capacitor with 5.0V DC applied is actually about 6μF. 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 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 AAT1142. 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. 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 capacitor should be placed in parallel with the low ESR, ESL bypass ceramic capacitor. This dampens the high Q network and stabilizes the system. Output Capacitor The output capacitor limits the output ripple and provides holdup during large load transitions. A 4.7μF to 10μF X5R or X7R ceramic capacitor typically provides sufficient bulk capacitance to stabilize the output during large load tran- sitions and has the ESR and ESL characteristics necessary for low output ripple. A smaller capacitor may result in slightly increased no load output regulation and output ripple with input voltages above 5V. This should be veri- fied under actual operating conditions. The output voltage droop due to a load transient is dom- inated 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 relationship of the output volt- age droop during the three switching cycles to the output capacitance can be estimated 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 4.7 F. 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. Thermal Calculations There are three types of losses associated with the AAT1142 step-down converter: switching losses, conduc- tion losses, and quiescent current losses. Conduction losses are associated with the R DS(ON) characteristics of the power output switching devices. Switching losses are dominated by the gate charge of the power output switch- ing devices. At full load, assuming continuous conduction mode (CCM), a simplified form of the losses is given by: PTOTAL IO 2 · (RDS(ON)H · VO + RDS(ON)L · [VIN - VO]) VIN + (tsw · FS · IO + IQ) · VIN

800mA Voltage-Scaling Step-Down Converter Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012 IQ is the step-down converter quiescent current. The term tsw is used to estimate the full load step-down con- verter switching losses. For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to: PTOTAL = IO 2 · RDS(ON)H + IQ · VIN Since RDS(ON), quiescent current, and switching losses all vary with input voltage, the total losses should be inves- tigated over the complete input voltage range. Given the total losses, the maximum junction tempera- ture can be derived from the  JA for the TDFN33-12 pack- age which is 50°C/W. TJ(MAX) = PTOTAL · ΘJA + TAMB Layout The suggested PCB layout for the AAT1142 is used to help ensure a proper layout. 1. The input capacitor should connect as closely as pos- sible to VIN and PGND. 2. C1 and L1 should be connected as closely as possi- ble. The connection of L1 to the LX pin should be as short as possible. 3. The feedback pin should be separate from any power trace and connected close to the VOUT terminal. Sensing along a high-current load trace will degrade VOUT load regulation. 4. The resistance of the trace from the GND terminal to PGND should be kept to a minimum. This will help to minimize any error in DC regulation due to differ- ences in the potential of the internal signal ground and the power ground. 5. Connect unused signal pins to ground to avoid unwanted noise coupling. When using S 2Cwire, con- nect SDA and SCL to ground to disable I2C function- ality. 6. Connect the exposed paddle (EP) to the GND plane. Manufacturer Part Number Inductance ( μH) Max DC Current (A) DCR ( ) Size (mm) LxWxH Type Table 3: Typical Surface Mount Inductors. Manufacturer Part Number Type Value Voltage Temp. Co. Case Murata GRM188R60J106ME47D Ceramic 10 6.3 X5R 0603 Murata GRM21BR60J106KE19L Ceramic 10 10 X5R 0805 Murata GRM188R60J475KE19D Ceramic 4.7 6.3 X5R 0603 Murata GRM21BR61A475KA73L Ceramic 4.7 10 X5R 0805 Table 4: Surface Mount Capacitors.

800mA Voltage-Scaling Step-Down Converter Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012

Ordering Information

Package Marking Part Number (Tape and Reel) TDFN33-12 AAT1142-1.2 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.

Package Information

Detail "A" Side View 3.00 ± 0.05 Index Area Detail "A" 1.70 ± 0.05 3.00 ± 0.05 0.05 ± 0.05 0.23 ± 0.05 0.75 ± 0.05 2.40 ± 0.05 Pin 1 Indicator (optional) 0.40 ± 0.05

0.1 REF

C0.3 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.

800mA Voltage-Scaling Step-Down Converter Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012 Copyright © 2012 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.