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Document overview

  • Manufacturer or author: Provided By digicamel.com
  • PDF pages: 19

Technical content

Features

  • Dual 3.0A Peak Output Current Regulators
  • 2.7V to 5.5V Input Voltage Range
  • Adjustable Output Voltage (0.6V to V IN)
  • 100% Duty-Cycle, Low-Dropout Operation
  • Integrated 120m Ω High-Side Power MOSFET
  • Integrated 85m Ω Low-Side Power MOSFET
  • Low Noise Light Load Mode
  • No External Compensation Required
  • Very Low 90 μA No-Load Operating Current
  • <1 μA Shutdown Current
  • Up to 95% Efficiency
  • 1.4MHz Switching Frequency
  • Overload and Short-Circuit Protection
  • Over-Temperature Protection
  • Internal Voltage Ramped Soft-Start
  • Temperature Range: -40°C to +85°C
  • 16-pin 3mm x 4mm TDFN Package

Applications

  • Digital Cameras and Camcorders
  • Netbooks and Nettops
  • Portable DVD and Media Devices
  • Power-Over-Ethernet
  • Set-Top Boxes Typical Application IN1 VCC1 AGND1 LX1 FB1PGND1 IN2 VCC2 PGND2 AGND2 LX2 FB2 EP EN1 EN2 VIN 2.7V to 5.5V VOUT1 0.6V to VIN VOUT2 0.6V to VIN ON/OFF ON/OFF AAT2522

Dual High-Current, Low-Noise, Step-Down Regulator DATA SHEET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012 Pin Descriptions Pin # Name Function 1 VCC2 Bias supply input for regulator #2.

2 EN2

Enable input for regulator #2. A logic high enables the second regulator of the AAT2522. A logic low forces regulator #2 into shutdown mode, placing the second output into a high-impedance state and reducing the VCC2 quiescent current to less than 1μA. 3 IN2 Power supply input for regulator #2.

4 EN1

Enable input for regulator #1. A logic high enables the primary regulator of the AAT2522. A logic low forces regulator #1 into shutdown mode, placing the primary output into a high-impedance state and reducing the VCC1 quiescent current to less than 1μA. 5 VCC1 Bias supply input for regulator #1. 6-7 IN1 Power supply input for regulator #1.

8 LX1

Inductor switching node for regulator #1. LX1 is the drain of the internal high-side P-channel and low-side N-channel MOSFETs. Externally connected to the power inductor as shown in the "Typical Application" drawing on page 1 of this datasheet. 9-10 PGND1 Power ground for regulator #1. PGND1 is internally connected to the source of the internal low-side N-channel MOSFET.

11 FB1

Feedback input for regulator #1. FB1 senses the output voltage for regulation control. Connect a resistive divider network from the output to FB1 to AGND1 to set the output voltage accordingly. The FB1 regulation threshold is 0.8V. 12 AGND1 Analog ground for regulator #1. AGND1 is internally connected to the analog ground of the control circuitry.

13 LX2

Inductor switching node for regulator #2. LX2 is the drain of the internal high-side P-channel and low-side N-channel MOSFETs. Externally connected to the power inductor as shown in the "Typical Application" drawing on page 1 of this datasheet. 14 PGND2 Power ground for regulator #2. PGND2 is internally connected to the source of the internal low-side N-channel MOSFET.

15 FB2

Feedback input for regulator #2. FB2 senses the output voltage for regulation control. Connect a resistive divider network from the output to FB2 to AGND2 to set the output voltage accordingly. The FB2 regulation threshold is 0.6V. 16 AGND2 Analog ground for regulator #2. AGND2 is internally connected to the analog ground of the control circuitry. EP AGND Substrate analog ground. Pin Configuration TDFN34-16 (Top View) IN2 EN1 VCC1 VCC2 EN2 IN1 IN1 LX1 PGND2 LX2 AGND1 AGND2 AGND FB2 FB1 PGND1 PGND1

Dual High-Current, Low-Noise, Step-Down Regulator DATA SHEET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012 Absolute Maximum Ratings Symbol Description Value Units VIN1, VIN2 IN1 to PGND1, IN2 to PGND2 -0.3 to +6 VVCC1, VCC2 VCC1 to AGND1, VCC2 to AGND2 -0.3 to +6 IINP1, IINP2 INPx RMS Current Capability ±3.0 A VLX1 LX1 to PGND1 -0.3 to (V IN1 + 0.3) VVLX2 LX2 to PGND2 -0.3 to (V IN2 + 0.3) ILX1, ILX2 LX RMS Current Capability ±5.0 A VEN1, VEN2 EN1 to AGND1, EN2 to AGND2 -0.3 to V IN VVFB1 FB1 to AGND1 -0.3 to (V FB1 + 0.3) VFB2 FB2 to AGND2 -0.3 to (V FB2 + 0.3) VGND AGND1 to PGND1, AGND2 to PGND2 -0.3 to +0.3 Thermal Characteristics Symbol Description Value Units TA Ambient Temperature Range -40 to +85 °CTJ Operating Junction Temperature Range -40 to +150 TSTORAGE Storage Temperature Range -65 to +150 TLEAD Maximum Soldering Temperature (at leads, 10 sec.) 300 Power SO-10 Thermal Impedance θJA Maximum Junction-to-Ambient Thermal Resistance 50 °C/W PD Maximum Power Dissipation 2 W

Dual High-Current, Low-Noise, Step-Down Regulator DATA SHEET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012 1. Specified by design.

Electrical Characteristics

CIN = 10μF, COUT = 22μF, L = 1.5μH. VIN1 = VIN2 = 3.6V, IN1 = VCC1 = EN1, IN2 = VCC2 = EN2, AGND = PGND. T A = -40°C to 85°C, unless otherwise noted. Typical values are at T A = 25°C. Symbol Description Conditions Min Typ Max Units VIN Input Voltage Range 2.7 5.5 V VOUT Output Voltage Range 0.6 V IN V Output Voltage Tolerance I OUT = 0 to 3A, VIN = 2.7V to 5.5V -3.0 +3.0 % VFB FB Regulation Threshold No Load, T A = 25°C 591 600 609 mV IQ No Load Supply Current Including IN1, VCC1, IN2, and VCC2 supply currents; No Load Current; not switching 90 180 μA ISHDN Shutdown Current EN = GND 1.0 μA IFB FB Leakage Current V FB = 1.0V 200 nA ΔVOUT(LOAD) Load Regulation 0A to 3A Load 0.5 % ΔVOUT/VIN Line Regulation V IN = 2.7V to 5.5V 0.2 %/V fOSC Oscillator Frequency 1.40 MHz tSS Soft-Start Period 150 μs Protection Features VUVLO Input Under-Voltage Lockout V IN Rising, Hysteresis = 0.25V 2.7 V TSHDN Over-Temperature Shutdown Threshold Hysteresis = 15°C 140 °C MOSFETs RDS(ON)HI High-Side P-Channel MOSFET On-Resistance 120 m Ω ILIMPK High-Side P-Channel MOSFET Current Limit 3.61 A RDS(ON)LO Low-Side N-Channel On-Resistance 85 m Ω Logic Input/Output Pins VEN EN Input Logic Threshold 0.6 1.4 V IEN EN Input Current 0V, V IN -1.0 +1.0 μA

Dual High-Current, Low-Noise, Step-Down Regulator DATA SHEET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012 Typical Characteristics Step-Down Converter Efficiency vs. Load (VOUT = 1.2V; L = 1.2µH) Output Current (mA) Efficiency (%) 0.1 1 10 100 1000 10000 100 VIN = 2.7V VIN = 3.0V VIN = 3.3V VIN = 3.6V VIN = 4.2V VIN = 5.0V VIN = 5.5V 0.1 1 10 100 Output Error (%) Output Current (mA) Step-Down Converter DC Regulation (VOUT = 1.2V; L = 1.2µH) 1000 1000 0 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 VIN = 2.7V VIN = 3.0V VIN = 3.3V VIN = 3.6V VIN = 4.2V VIN = 5.0V VIN = 5.5V Step-Down Converter Efficiency vs. Load (VOUT = 1.8V; L = 1.8µH) Output Current (mA) Efficiency (%) 0.1 1 10 100 1000 10000 100 VIN = 2.7V VIN = 3.0V VIN = 3.3V VIN = 3.6V VIN = 4.2V VIN = 5.0V VIN = 5.5V Step-Down Converter DC Regulation (VOUT = 1.8V; L = 1.8µH) Output Current (mA) Output Error (%) 0.1 1 10 100 1000 10000 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 VIN = 2.7V VIN = 3.0V VIN = 3.3V VIN = 3.6V VIN = 4.2V VIN = 5.0V VIN = 5.5V Step-Down Converter Efficiency vs. Load (VOUT = 2.5V; L = 2.5µH) Output Current (mA) Efficiency (%) 0.1 1 10 100 1000 10000 100 VIN = 3.3V VIN = 3.6V VIN = 4.2V VIN = 5.0V VIN = 5.5V Step-Down Converter DC Regulation (VOUT = 2.5V; L = 2.5µH) Output Current (mA) Output Error (%) 0.1 1 10 100 1000 10000 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 VIN = 3.3V VIN = 3.6V VIN = 4.2V VIN = 5.0V VIN = 5.5V

Dual High-Current, Low-Noise, Step-Down Regulator DATA SHEET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012 Typical Characteristics Step-Down Converter Efficiency vs. Load (VOUT = 3.3V; L = 3.3µH) Output Current (mA) Efficiency (%) 0.1 1 10 100 1000 10000 100 VIN = 3.6V VIN = 4.2V VIN = 5.0V VIN = 5.5V Step-Down Converter DC Regulation (VOUT = 3.3V; L = 3.3µH) Output Current (mA) Output Error (%) 0.1 1 10 100 1000 10000 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 VIN = 4.2V VIN = 5.0V VIN = 5.5V Step-Down Converter Line Regulation (VOUT = 1.2V; L = 1.2µH) Input Voltage (V) Accuracy (%) -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 IOUT = 0.10mA IOUT = 100mA IOUT = 1A IOUT = 1.5A IOUT = 2A IOUT = 3A Step-Down Converter Line Regulation (VOUT = 1.8V; L = 1.8µH) Input Voltage (V) Accuracy (%) -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 IOUT = 0.10mA IOUT = 100mA IOUT = 1A IOUT = 1.5A IOUT = 2A IOUT = 3A Step-Down Converter Output Voltage Error vs. Temperature (VIN = 3.6V; VOUT = 1.2V) Temperature (°C) Output Voltage Error (%) -50 -25 0 25 50 75 100 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 IOUT = 1A IOUT = 1.5A IOUT = 2A IOUT = 3A Step-Down Converter Output Voltage Error vs. Temperature (VIN = 3.6V; VOUT = 1.8V) Temperature (°C) Output Voltage Error (%) -50 -25 0 25 50 75 100 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 IOUT = 1A IOUT = 1.5A IOUT = 3A

Dual High-Current, Low-Noise, Step-Down Regulator DATA SHEET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012 Typical Characteristics Step-Down Converter Output Voltage Error vs. Temperature (VIN = 3.6V; VOUT = 2.5V) Temperature (°C) Output Voltage Error (%) -50 -25 0 25 50 75 100 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 IOUT = 1A IOUT = 1.5A IOUT = 3A Step-Down Converter Output Voltage Error vs. Temperature (VIN = 4.2V; VOUT = 3.3V) Temperature (°C) Output Voltage Error (%) -50 -25 0 25 50 75 100 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 IOUT = 1A IOUT = 1.5A IOUT = 2A IOUT = 3A No Load Input Current vs. Input Voltage (VEN1 = VEN2 = VIN) Input Voltage (V) Input Current (µA) 100 110 120 130 85°C 25°C -40°C Step-Down Converter Switching Frequency vs. Input Voltage (VOUT = 1.8V; IOUT = 1.5A) Input Voltage (V) Frequency Variation (%) Step-Down Converter Switching Frequency vs. Temperature (VIN = 3.6V; VOUT = 1.8V; IOUT = 1.5A) Temperature (°°C) Switching Frequency (MHz) -40 -20 0 20 40 60 80 100 1.20 1.25 1.30 1.35 1.40 1.45 1.50 1.55 1.60 Step-Down Converter Soft Start (VIN = 3.6V; VOUT = 1.8V; IOUT = 1.5A; CFF = 100pF) Time (100µs/div) Enable Voltage (top) (V) Output Voltage (middle) (V) Inductor Current (bottom) (A)

Dual High-Current, Low-Noise, Step-Down Regulator DATA SHEET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012 Typical Characteristics Step-Down Converter Load Transient Response (IOUT = 0.3A to 3.0A; VIN = 3.6V; VOUT = 1.2V; COUT = 22µF) Time (100µs/div) Output Voltage (bottom) (V) Output Current (top) (A) 0.8 1.0 1.2 1.4 0.3A 3.0A Step-Down Converter Load Transient Response (IOUT = 2.25A to 3.0A; VIN = 3.6V; VOUT = 1.2V; COUT = 22µF) Time (100µs/div) Output Voltage (bottom) (V) Output Current (top) (A) 0.8 1.0 1.2 1.4 2.25A 3.0A Step-Down Converter Load Transient Response (IOUT = 0.3A to 3.0A; VIN = 4.2V; VOUT = 3.3V; COUT = 22µF) Time (100µs/div) Output Voltage (bottom) (V) Output Current (top) (A) 2.9 3.1 3.3 3.5 3.7 0 0.3A 3.0A Step-Down Converter Load Transient Response (IOUT = 2.25A to 3.0A; VIN = 4.2V; VOUT = 3.3V; COUT = 22µF) Time (100µs/div) Output Voltage (bottom) (V) Output Current (top) (A) 2.9 3.1 3.3 3.5 2.25A 3.0A Step-Down Converter Line Transient Response (VIN = 3.6V to 4.3V; VOUT = 1.2V; IOUT = 3A) Time (200µs/div) Input Voltage (top) (V) Output Voltage (bottom) (V) 1.0 1.1 1.2 1.3 3.6V 4.3V Step-Down Converter Line Transient Response (VIN = 3.6V to 4.3V; VOUT = 1.8V; IOUT = 3A) Time (100µs/div) Input Voltage (top) (V) Output Voltage (bottom) (V) 1.6 1.7 1.8 1.9 2.0 3.6V 4.3V

Dual High-Current, Low-Noise, Step-Down Regulator DATA SHEET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012 Typical Characteristics Step-Down Converter Line Transient Response (VIN = 3.6V to 4.3V; VOUT = 2.5V; IOUT = 3A) Time (200µs/div) Input Voltage (top) (V) Output Voltage (bottom) (V) 2.1 2.3 2.5 2.7 2.9 3.6V 4.3V Step-Down Converter Output Ripple (VIN = 3.6V; VOUT = 1.2V; IOUT = 1mA) Time (100µs/div) Output Voltage (middle) (V) LX Voltage (top) (V) Inductor Current (bottom) (A) 1.18 1.20 1.22 0.0 0.2 0.4 3.6V Step-Down Converter Output Ripple (VIN = 3.6V; VOUT = 1.2V; IOUT = 3A) Time (500ns/div) Output Voltage (middle) (V) LX Voltage (top) (V) Inductor Current (bottom) (A) 1.18 1.20 1.22 2.5 3.0 3.5 3.6V Step-Down Converter Output Ripple (VIN = 4.2V; VOUT = 3.3V; IOUT = 1mA) Time (500ns/div) Output Voltage (middle) (V) LX Voltage (top) (V) Inductor Current (bottom) (A) 3.25 3.30 3.35 0.0 0.2 4.2V Step-Down Converter Output Ripple (VIN = 4.2V; VOUT = 3.3V; IOUT = 3A) Time (500ns/div) Output Voltage (middle) (V) LX Voltage (top) (V) Inductor Current (bottom) (A) 3.25 3.30 3.35 2.9 3.0 3.1 4.2V Step-Down Converter Short Circuit Protection (VIN = 5V; VOUT = 1.8V; CFF = 100pF) Time (100µs/div) LX Voltage (top) (V) Output Voltage (middle) (V) Inductor Current (bottom) (A) 0V1.8V

Dual High-Current, Low-Noise, Step-Down Regulator DATA SHEET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012 Functional Block Diagram EN1 PGND1 FB1 LX10.6V REF 0.6V REF IN1 Control Logic Control Logic VCC1 AGND1 INP Slope Comp Osc TSHDN EN2 PGND2 FB2 LX2 IN2 VCC2 AGND2 INP Osc TSHDN Slope Comp Functional Description The AAT2522 dual step-down regulators provide high- performance operation with a 1.4MHz switching frequen- cy. The AAT2522 regulators are completely independent, including separate power supply inputs and enable sig- nals. The highly integrated controller minimizes the external component requirements, optimizes efficiency over the complete load range, and produces reduced ripple and spectral noise. Apart from the small bypass input capacitor, only a small LC filter is required at the output. Typically, a 3.3μH inductor and a 22 μF ceramic capacitor are recommended for a 3.3V output (see table of recommended values). 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 high-side P-channel MOSFET (plus the DC drop of the external inductor and PCB layout). The device integrates extremely low R DS(ON) MOSFETs to achieve low dropout voltage during 100% duty cycle operation. This is advantageous in applications requiring high output voltages (typically > 2.5V) at low input voltages. The integrated low-loss MOSFET switches can provide greater than 85% efficiency at full load (5V Input to 3.3V Output). Light-load, low-noise operation maintains high efficiency, low ripple and low spectral noise with low cur- rent conditions (typically < 150mA). In battery-powered applications, as V IN decreases, the converter dynamically adjusts the operating frequency prior to dropout to maintain the required high duty-cycle and maintain accurate output regulation. The regulators will maintain output regulation until either the dropout voltage limit is exceeded, or the input under-voltage threshold is reached. The AAT2522 typically achieves better than ±0.5% out- put regulation across the input voltage and output load range. A current limit of 4.0A (typical) protects the IC and system components from short-circuit damage. Typical no load quiescent current is 90μA.

Dual High-Current, Low-Noise, Step-Down Regulator DATA SHEET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012 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. Soft start eliminates output voltage overshoot when the enable or the input voltage is applied. Under-voltage lockout prevents spurious start-up events. Control Scheme The AAT2522 regulators are peak current-mode, step- down converters. The controller senses the current through the high-side P-channel MOSFET for current loop control, as well as short-circuit and overload protec- tion. A fixed slope compensation signal is added to the sensed current to maintain stability for duty cycles greater than 50%. The resulting peak current-mode loop appears as a voltage-programmed current source in par- allel 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 reference voltage is internally set to program the con- verter output voltage greater than or equal to 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 AAT2522 into a low-power non-switching state. The total input current during shut- down is less than 1μA. Protection Circuitry 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. Input Under-Voltage Lockout Internal bias of all circuits is controlled via the VCC input. Under-voltage lockout (UVLO) guarantees suffi- cient V IN bias and proper operation of all internal cir- cuitry prior to activation. 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. Therefore, the inductor should be set equal to the output voltage numeric value in μH. This guarantees that there is sufficient internal slope compensation. 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 3.3μH CDRH6D38NP series Sumida inductor has a 15mΩ worst case DCR and a 3.5A DC current rating. With a 3A load, the inductor DCR conduction loss is 135mW, which gives less than 1.4% loss in efficiency for a 3A, 3.3V output. Output Capacitor Selection The output capacitor limits the output ripple and pro- vides holdup during large load transitions. A 10 μF to 22μF 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 domi- nated 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

Dual High-Current, Low-Noise, Step-Down Regulator DATA SHEET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012 responds. Within two or three switching cycles, the loop responds and the inductor current increases to match the load current demand. The first-order relationship of the output voltage droop during the three switching cycles to the output capacitance can be estimated by: COUT = 3 · ΔIO VDROOP · fSW 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 10 μF. 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. Input Capacitor Selection Select a 10μF to 22μF X7R or X5R ceramic capacitor for the input. To estimate the required input capacitor size, determine the acceptable input ripple level (V PK-PK) and solve for CIN. The calculated value varies with input volt- age and is a maximum when V IN is double the output voltage (VIN = 2x VO): CIN = and D =D · (1 - D) VO VIN - ESR · fSW VPKPK IO The peak ripple voltage occurs when V IN = 2x V O (50% duty cycle), resulting in a minimum output capacitance recommendation: CIN(MIN) = 1 - ESR · 4 · fSW VPKPK IO Always examine the ceramic capacitor DC voltage coef- ficient characteristics when selecting the proper value. For example, the derated capacitance of a 10 μF, 6.3V, X5R ceramic capacitor with 5.0V DC applied is actually about 6μF. The maximum input capacitor RMS current is: IRMS = IO · D · (1 - D) IRMS = IO · · 1 - 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: IO RMS(MAX)I occurs when V IN = 2 · VO The term D (1-D) appears in both the input voltage rip- ple 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 AAT2522. 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. The proper placement of the input capacitor (C1) can be seen in the evaluation board layout in the Layout section of this datasheet (see Figure 3). 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 should be placed in parallel with the low ESR/ESL bypass ceramic capacitor. This damp- ens the high Q network and stabilizes the system. Adjustable Feedback Network The output voltage on the AAT2522 is programmed with external resistors R OUT-FB and RFB-GND. To limit the bias cur- rent required for the external feedback resistor string while maintaining good noise immunity. Although a larger value will further reduce quiescent current, it will also increase the impedance of the feedback node, mak-

Dual High-Current, Low-Noise, Step-Down Regulator DATA SHEET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012 ing it more sensitive to external noise and interference. Therefore, the recommended value range for RFB-GND (R3 and R5 in Figure 2) is 100kΩ for good noise immunity or 221kΩ for reduced no load input current. The external resistor ROUT-FB (R2 and R4 in Figure 2), com- bined with an external 100pF feed forward capacitor (C 5 and C6 in Figure 2), delivers enhanced transient response for extreme pulsed load applications and reduces ripple in light load conditions. The addition of the feed forward capacitor typically requires a larger output capacitor OUT) for stability. The external resistors set the output voltage according to the following equation: VO = 0.6V · 1 + ROUT-FB RFB-GND or solving for ROUT-FB ROUT-FB = - 1 · RFB-GND VO 0.6V VOUT (V) R3 = R5= 100kΩ R2 = R4 (kΩ) 1.0 65.5 1.2 100 1.5 150 1.8 200 2.2 267 2.5 316 3.3 453 4.2 604 4.6 655 5 806 Table 1: Step-Down Converter Feedback Resistor Selection for Different Output Voltages. The typical circuit shown in the AAT2522 evaluation schematic is intended to be general purpose and suitable for most applications. In applications where transient load steps are more severe and the restriction on output voltage deviation is more stringent. To handle these cases some simple adjustments can be made. The sche- matic in Figure 2 shows the configuration for improved transient response in an application where the output is stepped down to 1.2V. The adjustments consist of adding an additional 22μF output capacitor, increasing the value of the feed forward capacitor C6 to 1nF, and adding the bias RC filter networks R1, C3 and R6, C4 in Figure 2. Applications Information Thermal Calculations There are three types of losses associated with the AAT2522 step-down converter: switching losses, con- duction losses, and quiescent current losses. Conduction losses are associated with the R DS(ON) characteristics of the power output switching devices: + RDS(ON)L · PLOSS(RES) = IO2 · RDS(ON)H · VO VIN VIN - VO VIN Switching losses are dominated by the gate charge of the power output switching devices. At full load, assum- ing continuous conduction mode (CCM), a simplified form of the switching losses is given by: PLOSS(SW) = tSW · fSW · IO · VIN The term tSW is used to estimate the full load step-down converter switching losses. Finally, the losses associated with the controller bias requirements are based the regulator’s quiescent current (I Q): PLOSS(BIAS) = IQ · VIN Summing the three power loss terms together provides the total power loss that the AAT2522 package must dis- sipate: PTOTAL = PLOSS(RES) + PLOSS(SW) + PLOSS(BIAS) For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to: + IQ · VINPTOTAL = IO2 · RDS(ON)H = VO 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.

Dual High-Current, Low-Noise, Step-Down Regulator DATA SHEET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012 Given the total losses, the maximum junction tempera- ture can be derived from the θJA for the TDFN34-16 package, which is 50°C/W. TJ(MAX) = PTOTAL · θJA + TAMB Assuming the operating ambient temperature is 85°C (the worst case), the maximum power dissipation for the TDFN34-16 package is determined in the following equa- tion: TJ(MAX) - TAMB PMAX = = 1.1WθJA 140°C - 85°C 50°C/W The power dissipation varies with the duty cycle and the output current of the converters. Given the maximum power dissipation of the TDFN34-16 package at 25°C and 85°C, the relationship between the maximum allow- able load for each channel and percent duty cycle are expressed in Figure 1. Maximum Output Current vs. Duty Cycle (VIN = 3.6V) Maximum Output Current (A) 02 0 4 0 6 0 8 010 30 50 70 90 100 Duty Cycle (%) 0.5 1.5 2.5 3.5 85°C 25°C Figure 1: Maximum Allowable Current for AAT2522 Step-Down Converters. As illustrated in Figure 1, the load limitation varies with the percentage of duty cycle and the operating ambient temperature. The total maximum load for both channels running at the same time in an 85°C ambient is about 4A (2A per channel). Therefore, if channel 1 is running at 1A, the maximum allowable load for channel 2 is no more than 3A to prevent the thermal shutdown. However, the maximum allowable load for each channel running at room temperature can increase up to 3A. In high current applications, the exposed pad needs to be connected to a thick power ground plane through vias for thermal dis- sipation. Layout Recommendations The suggested PCB layout for the AAT2522 is shown in Figures 3 and 4. The following guidelines should be used to help ensure a proper layout. 1. Place the input capacitor (C IN) as closely as possible to VIN and PGND. Split the input supply tray to separate the two input capacitors in order to prevent noise coupling between two channels at heavy load. 2. The output capacitor and inductor should be con- nected as closely as possible. The inductor connec- tion to the LX pin should be as short as possible. 3. The feedback trace or FB pin should be separated from any power trace and connected as closely as possible to the load point. Sensing along a high- current load trace will degrade DC load regulation. 4. The resistance of the trace from the load return 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.

Dual High-Current, Low-Noise, Step-Down Regulator DATA SHEET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012 AAT2522 Design Example Specifications VOUT1 = 3.3V @ 1A, Pulsed Load ILOAD = 1A VOUT2 = 1.2V @ 2A, Pulsed Load ILOAD = 2A VIN1 = 3.6V FS = 1.4MHz TAMB = 85°C in TDFN34-16 Package Step-Down Converter Output Inductor The internal slope compensation for the AAT2522 is set to 75% of the inductor current down slope for a 1.8V output and 1.8μH inductor: 0.75 · VO m = = = 0.75 L 0.75 · 1.8V 1.8μH A μs For 3.3V and 1.2V outputs, the inductor values are given in the following equations: 0.75 · VO L = = = 3.3μH; use 3.3μHm 0.75 · 3.3V 0.75A A μs 0.75 · VO L = = = 1.2μH; use 1.5μHm 0.75 · 1.2V 0.75A A μs For Sumida inductor, CDRH6D38NP-3R3N, 3.3μH, ISAT = 3.5A, DCR = 15mΩ. For Sumida inductor, CDRH4D22HPNP-1R5NC, ISAT = 3.9A, 1.5μH, DCR = 25mΩ. IPK1 = IOUT1 + ΔI1 = 1A + 0.03A = 1.03A2 IPK2 = IOUT2 + ΔI2 = 2A + 0.476A = 2.5A2

Dual High-Current, Low-Noise, Step-Down Regulator DATA SHEET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012 Step-Down Converter Output Capacitor VDROOP = 0.2V 1.5μH · 1.4MHz · 5.5V 23 RMS(MAX)I = · 3 · ΔILOAD VDROOP · FS 3 · 2A 0.2V · 1.4MHz COUT = = = 21.4μF; use 22μF

  • = 129mARMS VOUT2 · (VIN(MAX) - VOUT2) L · FS · VIN(MAX) PRMS = ESR · IRMS 2 = 5mΩ · (129mA)2 = 83μW Step-Down Converter Input Capacitor Input Ripple VPP = 50mV CIN = = = 9μF; use 10μF1 - ESR · 4 · FS VPP IO - 5mΩ · 4 · 1.4MHz50mV 0.2A IOUT 2RMSI P = ESR · (IRMS == 1 A AAT2522 Losses All values assume at 85°C ambient temperature and thermal resistance of 50°C/W in the TDFN34-16 package. PTOTAL PTOTAL + (tsw · FS · IOUT1 + IQ1) · VIN IOUT1 2 · (RDS(ON)H · VOUT1 + RDS(ON)L · [VIN -VOUT1]) VIN + (tsw · FS · IOUT2 + IQ2) · VIN IOUT2 2 · (RDS(ON)H · VOUT2 + RDS(ON)L · [VIN -VOUT2]) VIN PTOTAL = 0.58W 3.6V 3.6V TJ(MAX) = TAMB + ΘJA · PLOSS = 85°C + (50°C/W) · 0.58mW = 114°C

Dual High-Current, Low-Noise, Step-Down Regulator DATA SHEET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012 1. Sample stock is generally held on part numbers listed in BOLD. 2. 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.

Ordering Information

Package Marking Part Number (Tape and Reel) 1 TDFN34-16 9BXYY AAT2522IRN-1-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.

Package Information

3.000 ± 0.050 1.600 ± 0.050 0.050 ± 0.050 0.229 ± 0.051 (4x)

0.850 MAX

4.000 ± 0.050 3.300 ± 0.050 Index Area Detail "A" Top View Bottom View Side View 0.350 ± 0.100 0.230 ± 0.0500.450 ± 0.050 Detail "A" Pin 1 Indicator (optional) C0.3 All dimensions in millimeters.

Dual High-Current, Low-Noise, Step-Down Regulator DATA SHEET Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 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.