EV138 AAT1106 EVAL: 600mA Step-Down Converter Introduction The AAT1106 Evaluation Board contains a fully tested 600mA, 1.5MHz Step-Down DC/DC Regulator. The circuit has an input voltage range of 2.5V to 5.5V and four preset selectable outputs (1.2V, 1.5V, 1.8V and 2.5V). The device is capable of delivering up to 600mA of output current with a 3.0V VIN. The circuit can provide up to 96% efficiency and it consumes less than 1uA in shutdown mode. In light load mode operation there is very low output ripple voltage for noise sensitive applications. The AAT1106 comes in a small 5-pin TSOT23 package and the board has been optimized to fit small form factor designs. An optional TVS (SM6T6V8A) is connected between VIN and GND so that the evaluation board can be used in a hot-plug application. These features, plus the nominal operating frequency of 1.5MHz allowing the use of low profile surface mount components, make the AAT1106 evaluation board an ideal circuit for use in battery-powered, hand-held applications. Board Picture Figure 1: AAT1106 Evaluation Board. Layout Guidelines The following guidelines should be followed to ensure proper operation of the AAT1106: 1. The power traces, including the GND trace, LX-to-L1, L1-to-VOUT traces and the VIN-to-IN trace should be kept short, direct and wide to allow large current flow. Put many multiple-layer VIA pads when connecting traces between layers. 2. Connect the input capacitor C1 to the IN pin as close as possible to get good power filtering. 3. Keep the switching node, LX pin 3, away from the sensitive FB/OUT node. EV-138.2007.08.1.0 1 EV138 AAT1106 EVAL: 600mA Step-Down Converter JP1 U1 AAT1106 1 2.5V ~ 5.5V 4 VIN C1 4.7µH 5 EN GND 2 IN FB/VOUT LX L1 2.2µH 3 1.2V, 1.5V, 1.8V, 2.5V VOUT LX C3 10µH JP2 1 2 3 4 5 6 7 8 R2A 316k R2B 470k R2C 634k R2D 1M C2 22pF R1 316k Figure 2: AAT1106 Evaluation Board Schematic. Specification Input Voltage Output Error Voltage Output Current Test Conditions Min Typ Max Units 2.5 -3 0 3.6 5.5 +3 600 V % mA Table 1: AAT1106 Evaluation Board Specifications. 2 EV-138.2007.08.1.0 EV138 AAT1106 EVAL: 600mA Step-Down Converter Figure 3: AAT1106 Evaluation Board PCB Top Side. Figure 4: AAT1106 Evaluation Board PCB Bottom Side. Figure 5: AAT1106 Evaluation Board PCB Midlayer 1 Side. Figure 6: AAT1106 Evaluation Board PCB Midlayer 2 Side. Test Equipment 1. 2. 3. 4. 8.0V 5.0A laboratory power supply: Agilent E3648A or equivalent. Electronic Load: Agilent N3301A DC voltmeter: Agilent34401A or equivalent. Oscilloscope: Tektronix TDS3034B or equivalent. EV-138.2007.08.1.0 3 EV138 AAT1106 EVAL: 600mA Step-Down Converter Setup and Test (see connection diagram in Figure 7) A: Load and Line Regulation 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: VOUT and GND. 3. Before powering on the supply, set the FB setting jumper (JP2) to choose the VOUT voltage position (1.2V, 1.5V, 1.8V or 2.5V) and set the EN jumper (JP1) from OFF state to ON. 4. Vary the load from 0 to 600mA and the input voltage from 2.5V 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 ±3% of the nominal voltage. B: Ripple and Shutdown Current 1. Apply a DC power supply set to 3.6V at VIN. Set the output load current between 0 mA and 600 mA, and measure the output ripple voltage; the measurement should be less than 20 mVAC. 2. Apply a DC power supply set to 4.2V at VIN. Set the jumper from ON state to OFF. Measure the shutdown supply current at this point by removing the TVS device. The TVS (SM6T6V8A) is connected between VIN and GND. The supply current will be less than 1uA in shutdown. C: Short-Circuit 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 the output returns to its initial value. D: Enable Output 1. Short the EN pin to GND using JP1. The output will decay to zero. 2. Remove the short applied to the EN pin. The output will recover to its initial value. + +A+ + + V V - + Load - - A - Figure 7: AAT1106 Connection Diagram. 4 EV-138.2007.08.1.0 EV138 AAT1106 EVAL: 600mA Step-Down Converter Waveform A: Normal Waveform Condition: VIN = 3.6V, VOUT = 1.8V, No Load Ch1: LX, Ch2: IINDUCTOR, Ch3: VOUT (AC). Condition: VIN = 3.6V, VOUT = 1.8V, 1.2A Load Ch1: LX, Ch2: IINDUCTOR, Ch3: VOUT (AC). B: Startup time Condition: VIN = 3.6V, VOUT = 1.8V, 3Ω Load Ch1: EN, Ch2: IIN, Ch3: VOUT. EV-138.2007.08.1.0 5 EV138 AAT1106 EVAL: 600mA Step-Down Converter Component U1 L1 C1 C2 C3 R1, R2A R2B R2C R2D No Designator Part Number Description Manufacturer AAT1106 1.5 MHz, 600mA Synchronous Step-Down Converter Inductor 2.2UH 1.8A SMD Cap Ceramic 4.7µF16V X7R 10% 1206 Cap Ceramic 22pF 50V C0G 5% 0402 Cap Ceramic 10µF 16V X7R 10% 1206 Resistor 316KΩ 1/16W 1% 0402 SMD Resistor 470kΩ 1/16W 1% 0402 SMD Resistor 634KΩ 1/16W 1% 0402 SMD Resistor 1MΩ 1/16W 1% 0402 SMD 6.8V TVS Analogic Tech SF32-2R2M-R GRM42-6X7R475K16PT C1005COG1H220JT000P GRM31BR71C106KA01L Chip Resistor Chip Resistor (optional) Chip Resistor (optional) Chip Resistor (optional) SM6T6V8A (optional) Fenfa Murata TDK Murata ST Table 2: AAT1106 EVAL Bill of Materials. Output Voltage The board has an R1 value of 316kΩ. To adjust the output from the 1.8V default, select R2 according to Table 3 or use the jumper JP2. A smaller value resistor divider can be used for better noise immunity, values are shown in column 3. A larger value resistor divider is used as default for lower current consumption. Standard 1% resistor values are substituted for calculated values. VOUT (V) R1 = 316kΩ R2 (kΩ) R1 = 59kΩ R2 (kΩ) 0.6 0.80 1.00 1.20 1.30 1.40 1.50 1.60 1.70 1.80 0(short) 105 210 316 365 422 475 523 576 634 0(short) 19.6 39.2 59.0 68.1 78.7 88.7 97.6 107 118 VOUT (V) R1 = 316kΩ R2 (kΩ) R1 = 59kΩ R2 (kΩ) 0.6 1.90 2.00 2.10 2.20 2.32 2.40 2.50 3.30 0(short) 681 732 787 845 909 953 1000 1430 0(short) 127 137 147 158 169 178 187 267 Table 3: Resistor Selection for Adjustable Output Voltage. 6 EV-138.2007.08.1.0 EV138 AAT1106 EVAL: 600mA Step-Down Converter © Advanced Analogic Technologies, Inc. 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. 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AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders. Advanced Analogic Technologies, Inc. 3230 Scott Boulevard, Santa Clara, CA 95054 Phone (408) 737- 4600 Fax (408) 737- 4611 EV-138.2007.08.1.0 7