EV-103 AAT1152 EVAL 850kHz 1A Buck Regulator Introduction The AAT1152 MSOP evaluation board demonstrates performance, along with the suggested size and placement of external components, for the AAT1152 integrated buck regulator. The external components are selected for minimum size and optimum operation up to 1A output current. Please refer to the AAT1152 datasheet for more details about this product. Layout As with all switching power supplies, board layout for the AAT1152 is critical (see Figure 1). Special care has been taken with the placement of the external components. The input capacitor (C1) placement is critical and it must be located immediately adjacent to the AAT1152. As shown in Figure 2, the LX node trace has been routed under C1 in order to facilitate placement of C1 close to the IC. The output voltage feedback trace has been routed on the portion of backside of the board which has a ground plane on the top side (see Figure 3). The trace is routed to avoid the LX node and associated noise. Please refer to Table 1 for AAT1152 evaluation board specifications. R5 100k U1 AAT1152 VIN+ 5 C1 10µF POK R1 100 4 R2 3 100k C2 0.1µF 2 VP FB VCC EN POK LX SGND PGND 1 7 6 8 VO+ R3 R4 10k 1% L1 4.1µH C3-C5 3x 22µF 6.3V X5R VO- EN Figure 1: AAT1152 Evaluation Board Schematic. Specification Input Voltage Output Error Voltage Output Current Test Conditions Min Typ Max Units 2.7 3.6 ±3 5.5 V % A 0 1.0 Table 1: AAT1152 Evaluation Board Specification. EV-103.2005.07.1.1 1 EV-103 AAT1152 EVAL 850kHz 1A Buck Regulator Figure 2. AAT1152 Evaluation Board PCB Top Side. Figure 3. AAT1152 Evaluation Board PCB Bottom Side. Test Equipment 1. 6.0V 2.0A laboratory power supply: HP33401A or equivalent. 2. DC 0A to 1.0A load capable of operation down to 1.0V: Keithley 2400 or equivalent. When using the Keithley 2400, set the meter to 0V 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. Apply a DC power supply and DC voltmeter across input voltage terminals: VIN+ (positive terminal) and GND (negative terminal or return). 2. Apply a DC load and DC voltmeter to output terminals: VO+ and GND. 3. Vary the load from 0A to 1.0A and the input voltage from 2.7V to 5.5V while monitoring the output voltage. 4. The output voltage as measured at the output terminals of the evaluation board should not vary by more than ±3% of the nominal voltage. B: Short-Circuit and Over-Temperature Protection 1. Raise the input voltage to 5.5V 2. Apply a short from VO+ to GND at the evaluation board terminals. 3. Remove the short and verify that output returns to its initial value. C: Enable Input 1. Short the enable pin to GND. The output should decay to zero and the Power OK output should go low. 2. Remove the short applied to the enable pin. The output should recover to its initial value and the power OK output should return to the input voltage. 2 EV-103.2005.07.1.1 EV-103 AAT1152 EVAL 850kHz 1A Buck Regulator 1.500V Voltmeter Load 0-1A Power Supply 3.650V 0.147A 3.600V Voltmeter Figure 4: AAT1152 Connection Diagram. Component U1 U1 U1 U1 C3, C4, C5 C1 C2 R1 R2 L1 Part Number Description AAT1152IKS-1.0-T1 AAT1152IKS-1.8-T1 AAT1152IKS-2.5-T1 AAT1152IKS-3.3-T1 GRM21BR60J226KE19 GRM319R60J106KE01 GRM155R61A104KA01 Chip Resistor Chip Resistor CDRH5D18-4R1 1.0V 1A Buck Converter 1.8V 1A Buck Converter 2.5V 1A Buck Converter 3.3V 1A Buck Converter 22µF, 6.3V, X5R, 10%, 0805 10µF, 6.3V, X5R, 10%, 1206 0.1µF, 25V, X5R, 10%, 0402 100kΩ, 5%, 1/16W; 0402 100kΩ, 5%, 1/16W; 0402 4.1µH, 57mΩ, 1.95A Shielded AAT1152KS-1.0-T1 Table 3, 1%, 1/16W; 0402 AAT1152IKS-1.8-T1 0Ω, 0402 AAT1152IKS-2.5-T1 0Ω, 0402 AAT1152IKS-3.3-T1 0Ω, 0402 10kΩ, 1%, 1/16W; 0402 (required with AAT1152IKS-1.0-T1 when output is >1.0V only) R3 Chip Resistor R4 Chip Resistor Manufacturer AnalogicTech AnalogicTech AnalogicTech AnalogicTech MuRata MuRata MuRata Vishay Vishay Sumida Vishay Vishay Vishay Vishay Vishay Table 2: AAT1152 EVAL Bill of Materials. EV-103.2005.07.1.1 3 EV-103 AAT1152 EVAL 850kHz 1A Buck Regulator Output Voltage For an adjustable output, set R4 to 10kΩ and select R3 according to Table 3 using the AAT1152IKS-1.0-T1. VO (V) Ω) R3 (kΩ 1.0 1.1 1.2 1.25 1.3 1.4 1.5 1.6 1.7 1.8 1.85 1.9 2.0 2.1 2.2 2.3 2.4 2.5 3.3 0.00 (short) 1.00 2.00 2.55 3.01 4.02 4.99 6.04 6.98 8.06 8.45 9.09 10.0 11.0 12.1 13.0 14.0 15.0 23.2 Ω). Table 3: Resistor Selection for Adjustable Output Voltage (R4 = 10kΩ 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-103.2005.07.1.1