EV-108 AAT1151 MSOP EVAL 850kHz 700mA Buck Regulator Introduction The AAT1151 MSOP evaluation board demonstrates performance, along with the suggested size and placement of external components, for the AAT1151 integrated buck regulator. The external components are selected for minimum size and optimum operation up to 700mA output current. The output voltage can be adjusted with the use of the 1.0V version of the AAT1151 and external resistors R3 and R4. Please refer to the AAT1151 product datasheet for more details about this product. Layout As with all switching power supplies, the board layout for the AAT1151 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 AAT1151. 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 the back side 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 see Table 1 for AAT1151 MSOP evaluation board specifications. LX VIN+ VOUT+ AAT1151IKS 5 R1 100 4 VP FB VCC LX R3 1 7 Enable 3 R2 100k C7 0.1µF C1 10µF 2 EN LX GND PGND 6 8 R4 10.0k L1 3.3µH C2-C6 GND GND Figure 1: AAT1151 MSOP Evaluation Board Schematic. Specification Input Voltage Output Error Voltage Output Current Test Conditions Min Typ Max Units 2.7 -3 0 3.6 5.5 +3 700 V % mA Table 1: AAT1151 MSOP Evaluation Board Specifications. EV-108.2005.01.1.0 1 EV-108 AAT1151 MSOP EVAL 850kHz 700mA Buck Regulator Figure 2: AAT1151 MSOP Evaluation Board PCB Top Side. Figure 3: AAT1151 MSOP Evaluation Board PCB Bottom Side. Test Equipment 1. 6.0V 1.0A laboratory power supply: HP33401A or equivalent. 2. DC 0A to 700mA load capable of operation down to 1.0V: Keithley 2400 or equivalent. When using the Keithley 2400, set the meter to zero volts 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 0.7A 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 the output returns to its initial value. C. Enable Input 1. Short the enable pin to GND. The output should decay to zero. 2. Remove the short applied to the enable pin. The output should recover to its initial value. 2 EV-108.2005.01.1.0 EV-108 AAT1151 MSOP EVAL 850kHz 700mA Buck Regulator 1.500V Voltmeter Load 0 - 700mA Oscilloscope Power Supply 3.650V 0.147A 3.600V Voltmeter Figure 4: AAT1151 MSOP Connection Diagram. Component U1 U1 U1 C2-C61 C2-C61 C1 C7 R1 R2 Part Number Description AAT1151IKS-1.0-T1 AAT1151IKS-1.8-T1 AAT1151IKS-2.5-T1 GRM21BR60J106KE19 GRM21BR60J226KE39 GRM319R60J106KE01 GRM155R61A104KA01 Chip Resistor Chip Resistor 1.0V 700mA Adjustable Buck Converter 1.8V 700mA Buck Converter 2.5V 700mA Buck Converter 10µF, 6.3V, X5R, 10%, 0805 22uF, 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 AAT1151IKS-1.0-T1 Table 3, 1%, 1/16W; 0402 AAT1151IKS-1.8-T1 0Ω, 0402 AAT1151IKS-2.5-T1 0Ω, 0402 10kΩ, 1%, 1/16W; 0402 (AAT1151IKS-1.0-T1 only) 3.3µH 85mΩ 1.1A Shielded Inductor R3 Chip Resistor R4 Chip Resistor L1 CDRH3D16-3R3 Quantity Manufacturer 1 1 1 4 2 1 1 1 1 1 1 1 1 AnalogicTech AnalogicTech AnalogicTech MuRata MuRata MuRata MuRata Vishay Vishay Vishay Vishay Vishay Vishay 1 Sumida Note 1. Either 4x 10µF or 2x 22µF capacitors can be used for C3-C7. Table 2: AAT1151 MSOP EVAL Bill of Materials. EV-108.2005.01.1.0 3 EV-108 AAT1151 MSOP EVAL 850kHz 700mA Buck Regulator Output Voltage For an adjustable output with the AAT1151IKS-1.0-T1, set R4 to 10kΩ and select R3 according to Table 3. When using a fixed output version of the AAT1151, R3 is a short and R4 is omitted. 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 for AAT1151IKS-1.0-T1 (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-108.2005.01.1.0