EV-106 AAT1143EVAL 1MHz 0.4A Buck Converter Introduction The AAT1143 evaluation board demonstrates performance, as well as suggested size and placement of external components, for the AAT1143 integrated buck regulator. The external components are selected for minimum size and optimum operation up to 400mA output current. Resistors R1 and R2 set the output voltage. For improved transient response, a 100pF to 150pF capacitor can be used for C4, along with increasing the value of C1 to 10µF. C3 is available for cases where additional external compensation is necessary; for most applications it is not used. Refer to the AAT1143 datasheet for more details about this product. Layout As with all switching power supplies, the board layout for the AAT1143 is critical (see Figure 1). Special care has been taken with the placement of external components. The input capacitor (C2) placement is critical. It must be placed immediately adjacent to the AAT1143. As shown in Figure 2, the output voltage feedback trace has been routed on the portion of the back side of the board which has a ground plane on the top side (see Figure 3). The trace is also routed to avoid the LX node and associated noise. Resistors R1 and R2 are placed as closely as possible to the AAT1143 in order to minimize the length of the trace for the high impedance node associated with the OUT pin. This minimizes the potential for external noise associated with the power stage of the AAT1143 and other circuitry coupling into the feedback of the AAT1143. Please refer to Table 1 for AAT1143 evaluation board specifications. INTERNAL DOCUMENT DO NOT COPY 1 2 3 Enable VIN C4 U1 AAT1143 1 R1 VOUT 2 3 L1 C1 4.7µF 4 C3 R2 59k EN PGND OUT PGND VIN PGND LX AGND 8 7 6 5 C2 4.7µF GND GND LX Figure 1: AAT1143 Evaluation Board Schematic for Enhanced Transient Response Version; C4 = 100pF; C1 = 10µF. Specification Input Voltage Output Error Voltage Output Current Test Conditions Min Typ Max Units 2.7 -3 0 3.6 5.5 +3 0.4 V % A Table 1: AAT1143 Evaluation Board Specifications. EV-106.2005.04.1.1 1 EV-106 AAT1143EVAL 1MHz 0.4A Buck Converter Figure 2: AAT1143 Evaluation Board PCB Top Side. Figure 3: AAT1143 Evaluation Board PCB Bottom Side. Test Equipment INTERNAL DOCUMENT DO NOT COPY 1. 6.0V 1.0A laboratory power supply: HP33401A or equivalent. 2. DC 0 to 0.4A electronic load, capable of operation down to 0.6V: Keithley 2400 or equivalent. (When using the Keithley 2400, set the meter to operate in voltage source mode and set the load current by varying the current compliance [maximum current] of the meter.) 3. DC voltmeter: HP34401A or equivalent. 4. Oscilloscope: Tektronix TDS744A or equivalent. Setup and Test A: Load and Line Regulation (see connection diagram in Figure 4) 1. Short (apply jumper to) Pins 2 and 3 of the enable connector. 2. Apply a DC power supply and DC voltmeter across input voltage terminals: VIN (positive terminal) and GND (negative terminal or return). 3. Apply a DC load and DC voltmeter to output terminals VOUT and GND. 4. Vary the load from 0 to 0.4A and the input voltage from 2.7V to 5.5V while monitoring the output voltage. 5. The output voltage as measured at the output terminals of the evaluation boards should not vary by more than ±1% of the nominal voltage. B: Short-Circuit and Over-Temperature Protection 1. Raise the input voltage to 5.5V. 2. Apply a short from VOUT to GND at the evaluation board terminals. 3. Remove the short and verify that output returns to its initial value. C: Enable Input 1. Remove the jumper from Pins 2 and 3 of the enable connector and apply to Pins 1 and 2. The output should decay to zero. 2. Remove the short and replace the short from Pins 2 to 3 of the enable connector. The output should recover to its initial value. 2 EV-106.2005.04.1.1 EV-106 AAT1143EVAL 1MHz 0.4A Buck Converter 3.600V Voltmeter 1.500V Voltmeter Power Supply 3.650V 0.147A Load 0-400mA Oscilliscope Figure 4: AAT1143 Connection Diagram. Component U1 C2 Part Number Description AAT1143IJS-0.6-T1, AAT1143IJS-1.5-T1 GRM319R60J476KE01 GRM319R60J476KE01 GRM319R60J106KE01 1MHz 0.4A Buck Converter 4.7µF, 10V, X5R, 10%, 0805 4.7µF, 10V, X5R, 10%, 0805 10µF, 6.3V, X5R, 10%, 0805 (optional for improved transient response1) See Table 3, 1%, 1/16W, 0402 59.0kΩ, 1%, 1/16W, 0402 4.7µH, 105mΩ, 900mA, Shielded 10µH, 210mΩ, 550mA, Shielded (see Table 3) 100pF, 25V, C0G, 10%, 0402 (optional for improved transient response1) N/A Manufacturer AnalogicTech INTERNAL DOCUMENT DO NOT COPY C1 R1 R2 C4 Chip Resistor Chip Resistor CDRH3D16-4R7 CDRH3D16-10R Chip Capacitor C3 Chip Capacitor L1 MuRata MuRata Vishay Vishay Sumida Vishay Vishay Table 2: AAT1143 EVAL Bill of Materials. 1. For improved transient response version, add C4 and increase C1 to 10µF. EV-106.2005.04.1.1 3 EV-106 AAT1143EVAL 1MHz 0.4A Buck Converter Output Voltage For an adjustable output, set R2 to 59kΩ and select R1 according to Table 3. VO (V) Ω) R1 (kΩ L1 (µH) 0.6 0.8 1.0 1.5 1.6 1.7 1.8 2.5 0 19.6 39.2 88.7 97.6 110 118 187 4.7 4.7 4.7 4.7 4.7 4.7 4.7 10 INTERNAL DOCUMENT DO NOT COPY Ω). Table 3: Component Selection for Adjustable Output Voltage (R2 = 59.0kΩ AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. AnalogicTech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with AnalogicTech’s standard warranty. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed. Advanced Analogic Technologies, Inc. 830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737-4600 Fax (408) 737-4611 4 EV-106.2005.04.1.1 Form#: FOR001 Rev. D