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EV154EVALUATION BOARD DATA SHEET

Evaluation Board for the AAT1275 Boost Converter with USB Power Switch

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202277A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 17, 2012

IntroductionThe AAT1275 evaluation board provides a platform for test and evaluation of the AAT1275 switching boost converter with USB Power Switch. The evaluation board demonstrates suggested size and placement of external components to achieve 5V output voltages and up to 500mA output load current to support USB VBUS operation from an input supply as low as 2.7V. The external components are selected for small size to suit portable applications while the layout has been optimized to achieve high efficiency and low output noise with the TSOPJW-12 package. The design operates across an input voltage range from 2.7 to 5V.

This document provides details on the operation and test of the AAT1275 Evaluation Board. Modification of the resistor divider network (R2, R3) allows different output voltages. The load switch current limit level at OUT2 is determined by RSET (R4) value (see Table 1). When the OUT2 pin load current has exceeded current limit level the AAT1275 shuts down to minimize the power dissipation and component stresses under over load and short circuit conditions.

Schematic and BOM

LIN1

VIN2 PGND 3

SW4

OUT1 5

OUT2 6

SET7

FLT 8

FB 9

GND10

VCC11

EN 12

AAT1275U1

432kΩR2

59kΩR3

10kΩR1

R4

16.9kΩ

L1 2.2µH

C24.7µF10V

C34.7µF

10V

C6120µFCCase

C14.7µF

FLT

VIN

GND

123

Enable

VIN

VIN

VO2VO1

J5GND

GND

Figure 1: AAT1275 Evaluation Board Schematic (AAT1275-DB1)

Symbol DescriptionU1 AAT1275 TSOPJW-12L1 2.2μH, CDRH2D14-2R2 Sumida 3.2x3.2x1.55mm, 94mΩ

C1, C2, C3, C5 4.7μF 10V 0805C4 100pF 10V 0402C6 120μF 10V (optional)R1 10kΩ 1% 0402R2 432kΩ 1% 0402R3 59kΩ 1% 0402R4 16.9kΩ 1% 0402R5 10Ω 1% 0402

Table 1: AAT1275 Bill of Materials.

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Test Equipment1. Unit under test (UUT) is the AAT1275 Evaluation Board.2. One (1) XT30-2 Power Supplies or equivalent.3. HP6060B DC Electronic Load or equivalent. 4. Two (2) Fluke 189 DC voltmeters or equivalent. Set to DCV setting.5. Oscilloscope Tektronix TDS3054B or equivalent, three (3) Tek P6139A oscilloscope voltage probes or equivalent,

and one Tektronix TCP202 300V 15A peak current probe. 6. Line Transient and Load Transient boards.7. Miscellaneous test leads (banana plug to clip lead type is recommended).

Setup and Test

Test: Load Switch Current Limit versus RSET

1. Configure the specified test equipment as shown in Figure 2.2. Enable the UUT jumper JP1 to the ‘ON’ position.3. Set the HP6060B DC Electronic Load to Constant Voltage Mode (CV) and clamp its voltage at 4.9V. 4. Turn on input power supply and set to the designed voltage (4.0V) while monitoring the VOUT2, and IOUT2 on the

oscilloscope.5. Vary the clamped voltage on the HP6060B DC Electronic Load with different values (4.8V, 4.7V, …,4.0V) until the

VOUT2 and IOUT2 turn OFF and ON periodically.6. Use horizontal cursors to measure the Load Switch Current Limit on the oscilloscope.7. Repeat step 2 to 5 for different values of RSET (R4) in Table 2 below.

RSET (KΩ) IOUT (mA)11 74012 69014 59016 55018 45020 42030 16040 100

Table 2: Load Switch Current versus RSET.

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Figure 2: AAT1275 Evaluation Board Connection Diagram for Load Switch Current Limit Measurement.

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Test: Load and Line Regulation1. Configure the specified test equipment as shown in Figure 3.2. Enable the UUT jumper JP1 to the ‘on’ position. 3. Turn on the input power supply and set to desired input voltage based on the DC voltmeter.4. Vary the output load from 0 to 500mA and vary the input voltage from 2.7V to 5V while monitoring the output

voltage.

Figure 3: AAT1275 Evaluation Board Connection Diagram for Load and Line Regulation Measurement.

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Test: Start up using Enable 1. Configure the specified test equipment as shown in Figure 4.2. Set the Oscilloscope to single sequence, and trigger the rising edge of VOUT.3. Turn on input power supply and toggle EN to “ON” position while monitoring the EN, VOUT1, VOUT2, and IIN on the

oscilloscope.4. Repeat step #2 and step #3 for different IOUT, and VIN.

Figure 4: AAT1275 Evaluation Board Connection Diagram for Start Up Measurement.

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Test: Output Ripple Measurement1. Configure Oscilloscope CH1 for output ripple measurement. Plug probe into CH1 as shown in Figure 4. a. AC Coupling, 25mV/div. b. BW≤100MHz to limit high frequency pickup2. Configure Oscilloscope auto-trigger.3. Turn on input power supply. Set input voltage between 2.7 and 5V and adjust output load from 0 to 500mA, as

desired. It should be noted that light load measurements (<20mA) may be affected by electronic load character-istics. As an alternative, parallel arrangement of 1/4W carbon film resistor(s) can be used.

4. To minimize high frequency noise pickup due to PCB parasitic and guarantee consistent results, CH1 output ripple should be measured directly across output capacitor C1, as shown in Figure 3. Probe tip contacting capacitor posi-tive terminal. Probe ground consisting of a small bus wire wrapped around probe ground (see Figure 4).

Probe GND

Probe Tip

Bus wire wrapped aroundprobe ground, with probe

spring tip removed

Figure 5: Oscilloscope Probe Setup for Output Ripple Measurement.

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Test: Line Transient Response1. Configure the specified test equipment as shown in Figure 6.2. Enable UUT by connecting the jumper to the ‘on’ position. 3. Use Line Transient Response Board to generate the input voltage step by setting the first power supplies to 3.6V

and the second one to 4.2V. 4. Toggle the input voltage from 3.6V to 4.2 V by setting the magnitude of the PWM to 5Vpp at 5MHz while monitor-

ing the AC input voltage and the AC output voltage on the oscilloscope.5. Repeat step #4 for different input voltage steps.

Figure 6: AAT1275 Evaluation Board Connection Diagram for Line Transient Measurement.

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Test: Load Transient Response1. Configure the specified test equipment as shown in Figure 7.2. Enable UUT by connecting the jumper to the ‘on’ position. 3. Generate the step output current using a PWM (set VPP = 5V at 5KHz), a Power MOSFET, and adjustable resistors

(R7, R8).4. Adjust R7 and R8 to get the designed step output current while monitoring the step output current and the output

voltage response (AC coupling) on the oscilloscope.5. Repeat step #4 for different output current steps and over the ranges of VIN.

Figure 7: AAT1275 Evaluation Board Connection Diagram for Load Transient Measurement.

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Printed Circuit Board

Figure 8: Top Layer (not to scale).

Figure 9: Bottom Layer (not to scale)

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Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved.

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