EV-139 AAT1149 EVAL: 3MHz Fast Transient 400mA Step-Down Converter Introduction The AAT1149 Evaluation Board provides a platform for test and evaluation of the AAT1149 3MHz Fast Transient 400mA Step-Down Converter. The evaluation board demonstrates suggested size and placement of external components to achieve the best performance. The external components are limited and selected for small size to suit portable device applications while the layout has been optimized to achieve high efficiency and low output noise with the SC70JW-8 package. The design operates across an input voltage range from 2.7V to 5.5V. The AAT1149 Evaluation Board provides an adjustable output voltage from 1V to VIN at 400mA maximum output current. Resistors R1 and R2 program the output to regulate at a voltage higher than 0.6V. The suggested value for R2 is 59kΩ. Table 2 summarizes the resistor values for various output voltages. Connecting EN to IN will turn on the part while connecting EN to GND will disable the part. Schematic and BOM SC70JW-8 L1 1.8μH 4 3 IN VIN LX VOUT R1 Adj. ON/OFF C2 4.7μF 1 C6 100pF 2 FB EN (Optional) AAT1149 6 7 PGND AGND PGND PGND 5 R2 59K C1 4.7μF 8 Figure 1: AAT1149 Evaluation Board Schematic. Symbol Description U1 C1, C2, C3 L1 R1 R2 AAT1149 SC70JW-8 4.7μF 10V 0805 100pF 10V 0402(Optional) 1.8µH Sumida CDRH2DO9 See Table 2; 10V 0402 59kΩ 10V 0402 Table 1: AAT1149 Evaluation Board Build of Materials (BOM). EV-139.2007.08.1.0 1 EV-139 AAT1149 EVAL: 3MHz Fast Transient 400mA Step-Down Converter VOUT (V) R2 = 59kΩ R1 (kΩ) R2 = 221kΩ R1 (kΩ) 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.8 1.85 2.0 2.5 3.3 3.6 19.6 29.4 39.2 49.9 59.0 68.1 78.7 88.7 118 124 137 187 267 295 75 113 150 187 221 261 301 332 442 464 523 715 1000 1105 Table 2: AAT1149 Adjustable Resistor Values. Test Equipment 1. 2. 3. 4. 5. 6. 7. Unit under test (UUT) is the AAT1149 Evaluation Board. One (1) Keithley 2430 3A source meter or equivalent. Two (2) XT30-2 power supplies or equivalent. Two (2) 10Ω, 100W variable resistors, or DC electronic loads. Two (2) Fluke 189 multi-meters or equivalent. A HP33120A 15MHz Function/ Arbitrary waveform generator. Set to PWM setting. Oscilloscope Tektronix TDS3054B or equivalent, three (3) Tek P6139A oscilloscope voltage probes or equivalent, and one Tektronix TCP202 300V 15A peak current probe. 8. A Network Analyzer. 9. Miscellaneous test leads (banana plug to clip lead type is recommended). 2 EV-139.2007.08.1.0 EV-139 AAT1149 EVAL: 3MHz Fast Transient 400mA Step-Down Converter Setup and Test Test: Line-Load Regulation 1. 2. 3. 4. Configure the specified test equipment as shown in Figure 2. Enable UUT by connecting the jumper to the ‘ON’ position. Turn on the input power supply and set to desired input voltage based on the DC voltmeter. Vary the output load from 0 to 400mA and vary the input voltage from 2.7V to 5.5V while monitoring the output voltage. 5. % Error = VOUT - VNOMINAL where VNOMINAL is the output voltage at 10mA output current. VNOMINAL Figure 2: AAT1149 Evaluation Board Connection Diagram for Line and Load Regulation. EV-139.2007.08.1.0 3 EV-139 AAT1149 EVAL: 3MHz Fast Transient 400mA Step-Down Converter Test: Line Transient Response 1. Configure the specified test equipment as shown in Figure 3. 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 supply to 3.6V and the second one to 4.2V. 4. Toggle the input voltage from 3.6V to 4.2V by setting the magnitude of the PWM to 5Vpp at 5MHz while monitoring the AC input voltage and the AC output voltage on the oscilloscope. 5. Repeat step 4 for different input voltage steps and over the range of VOUT. Vin(AC) Vout(AC) Figure 3: AAT1149 Evaluation Board Connection Diagram for Line Transient Response. 4 EV-139.2007.08.1.0 EV-139 AAT1149 EVAL: 3MHz Fast Transient 400mA Step-Down Converter Test: Load Transient Response 1. Configure the specified test equipment as shown in Figure 4. 2. Enable UUT by connecting the jumper to the ‘ON’ position. 3. Generate the step output load 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 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 and VOUT. Iload Vout(AC) Figure 4: AAT1149 Evaluation Board Connection Diagram for Load Transient Response. EV-139.2007.08.1.0 5 EV-139 AAT1149 EVAL: 3MHz Fast Transient 400mA Step-Down Converter Test: Quiescent Current vs. Input Voltage 1. 2. 3. 4. Configure the specified test equipment as shown in Figure 5. Enable UUT by connecting the jumper to the ‘ON’ position. Remove the output loads (open circuit). Replace the input power supply by Keithley 2400 3A source meter or equivalent. Set VSRC to the designed input voltage (VSRC = VOUT + 1V), and set the ICOM to 200µA. 5. Turn on the Keithley and read the compliance current (quiescent current). 6. Vary the input voltage VSRC = VOUT + 1V while monitoring the corresponding compliance current. Figure 5: AAT1149 Evaluation Board Connection Diagram for Quiescent Current. 6 EV-139.2007.08.1.0 EV-139 AAT1149 EVAL: 3MHz Fast Transient 400mA Step-Down Converter Test: Startup Using Enable 1. Configure the specified test equipment as shown in Figure 6. 2. Set the oscilloscope to single sequence, and trigger the rising edge of VOUT. 3. Turn on input power supply and toggle EN to the “ON” position while monitoring the EN, VOUT, LX, and ILOAD on the oscilloscope. 4. Repeat steps 2 and 3 for different IOUT, VIN, and VOUT. Test: Startup using VIN 1. 2. 3. 4. 5. Configure the specified test equipment as shown in Figure 6. Enable UUT by connecting the jumper to the “ON” position. Set the oscilloscope to single sequence, and trigger the rising edge of VOUT. Disconnect VIN to input power supply. Turn on input power supply and toggle VIN by connecting the banana clip to the power supply while monitoring the VIN, VOUT, LX, and ILOAD on the oscilloscope. 6. Repeat steps 3 through 5 for different IOUT, VIN, and VOUT. Figure 6: AAT1149 Evaluation Board Connection Diagram for Startup. EV-139.2007.08.1.0 7 EV-139 AAT1149 EVAL: 3MHz Fast Transient 400mA Step-Down Converter Test: Efficiency vs. Output Current 1. Configure the specified test equipment as shown in Figure 7. Connect voltmeters as closely as possible to the input and output capacitors to avoid voltage drop along the trace resistance. 2. Enable UUT by connecting the jumper to the “ON” position. 3. Set Keithley load to 4 Wire Sensing Mode (the two sensing wires should connect as closely as possible to the output cap. 4. Vary the output current (IOUT = ISRC) from -1mA to -400mA and keep the input voltage the same while monitoring the input current (IIN), and the output voltage (VOUT). 5. Calculate the efficiency as the following equation: Efficiency = η% = 100 · (VOUTIOUT) VINIIN 6. Repeat steps 4 and 5 for different input and output voltages. Figure 7: AAT1149 Evaluation Board Connection Diagram for Efficiency vs. Load Current. 8 EV-139.2007.08.1.0 EV-139 AAT1149 EVAL: 3MHz Fast Transient 400mA Step-Down Converter Test: RDS(ON)H and RDS(ON)L 1. Configure the specified test equipment as shown in Figure 8. 2. Enable UUT by connecting the jumper to the ‘ON’ position, and connect the FB pin to GND to turn-on the high side PMOS and turn-off the low side NMOS. 3. Connect 4 wires (Force and Sense) from the Keithley power supply between VIN and LX node. Set the compliance to VSRC = 40mV at ICOMP = 300mA. 4. Power up and measure RDS(ON)H = VSRC ICOMP 5. To measure the RDS(ON)L, repeat steps 2 through 4 with the FB pin connected to VCC (to turn on the low side NMOS) and connect the 4 wires (Force and Sense) between LX and GND. RDS(ON)L = VSRC ICOMP Figure 8: AAT1149 Schematic Connection Diagram for RDS(ON). EV-139.2007.08.1.0 9 EV-139 AAT1149 EVAL: 3MHz Fast Transient 400mA Step-Down Converter Test: Gain and Phase Margin (Loop Gain) 1. Break the feedback loop and insert a one-to-one isolation transformer between the broken original connection. Configure the specified test equipment as shown in Figure 9. 2. Inject a signal from SOURCE OUT to the loop through the isolation transformer while monitoring the ratio of CHA and CHB on the Network Analyzer. 3. Set the output current to heavy load while monitoring the LX node of the converter on the oscilloscope (to obtain a good result the converter must be in continuous PWM mode). 4. Sweep the frequency from SOURCE OUT of the Network Analyzer from 10Hz to 1MHz and adjust the magnitude of the injected signal (around 10mV to 100mV) in order to have a clean PWM waveform at the LX node. 5. Repeat the measurement for different VIN, VOUT, and ILOAD. L1 1.8uH 50 4 Isolation Transformer LX 3 VIN IN R1 Adj. ON/OFF 1 EN FB C6 100pF 2 (Optional) R2 59K C2 4.7uF VOUT Broken Original Connection 6 C1 5 PGND AGND PGND PGND 7 4.7uF 8 Figure 9: AAT1149 Schematic Connection Diagram for Gain and Phase Margin. 10 EV-139.2007.08.1.0 EV-139 AAT1149 EVAL: 3MHz Fast Transient 400mA Step-Down Converter Printed Circuit Board Figure 10: AAT1149 Evaluation Board Top Layer (not to scale). Figure 11: AAT1149 Evaluation Board Bottom Layer (not to scale). © 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. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice. Except as provided in AnalogicTech’s terms and conditions of sale, AnalogicTech assumes no liability whatsoever, and AnalogicTech disclaims any express or implied warranty relating to the sale and/or use of AnalogicTech products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. In order to minimize risks associated with the customer’s applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. 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. 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-139.2007.08.1.0 11