EV-134 AAT4252A EVAL Dual Slew Rate Controlled Load Switch Introduction The AAT4252A evaluation board provides a platform for test and evaluation of the AAT4252A dual slew rate controlled load switch. 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 devices applications while the layout has been optimized to achieve optimum thermal characteristics with the TDFN22-8 package and low inductive output ringing with the fast slew rate setting. The design operates across an input voltage range from 1.5 to 6.5V. The AAT4252A evaluation board provides dual inputs and outputs at 65μs and 600μs turn-on slew rate. The desired turn-on slew rate time is determined by setting the logic level of the FAST pin. Connecting the FAST pin to logic high (VIN) sets the output to fast turn-on slew rate while logic low (GND) sets the output to slow turn-on slew rate. Connecting ENA or ENB to a PWM function generator allows the turn-on slew rate features to work properly while connecting ENA or ENB to GND will disable either A or B channel. This document provides details on the operation and test of the AAT4252A evaluation board with a single or separate input power supplies by using the JP1 jumper. Schematic and BOM TSOPJW-12 INA 2 JP1 5 INB 3 ENA C1 C2 1μF 1μF OUTA 12 OUT A INB OUTB 7 OUTB ENA AAT4252A 1 FAST INA FAST N/C 4 ENB ENB C3 C4 0.1μF 0.1μF 6 GND 8,9,10,11 Figure 1: AAT4252A Evaluation Board Schematic (AAT4252A ITP-DB1) Symbol Description U1 C1 C2 C3 C4 AAT4282A TSOPJW-12 1μF 10V 0603 1μF 10V 0603 0.1μF 10V 0603 0.1μF 10V 0603 Table 1: AAT4252A Evaluation Board Bill of Materials (BOM) EV-134.2007.06.1.0 1 EV-134 AAT4252A EVAL Dual Slew Rate Controlled Load Switch Test Equipment 1. 2. 3. 4. 5. 6. 7. Unit under test (UUT) is the AAT4252A 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 two DC electronic loads. Two (2) Fluke 189 DC voltmeters or equivalent. Set to DCV setting. One (1) 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. Miscellaneous test leads (banana plug to clip lead type is recommended). Setup and Test Test: RDS(ON) over VIN using Keithley V/I source 2430 1. Configure the specified test equipment as shown in Figure 2 2. Connect a floating Kelvin pulse from Keithley V/I source between INA and OUTA (with VIN as positive side); set the voltage pulse to 1V with 5ms pulse width, and set compliance to 100mA (the two sensing output wires need to connect as closely as possible to the INA and OUTA pins.) 3. Remove JP1 jumper to disconnect INA and INB; enable ENA and FAST by setting JP2 and JP4 to INA, and disable ENB by setting JP3 to GND. 4. Turn on the input power supply and set to the desired input voltage based on the DC voltmeter. 5. Power up the Keithley V/I source and read the voltage (VDS) and the current (IDS) measurements on the Keithley V/I source. 6. Vary the input voltage from 1.8 to 5.5V to observe RDS(ON) at different input voltages. 7. Repeat steps 1 through 6 with different compliance current from 100mA to 2A. 2 EV-134.2007.06.1.0 EV-134 AAT4252A EVAL Dual Slew Rate Controlled Load Switch Figure 2: AAT4252A Evaluation Board Connection Diagram EV-134.2007.06.1.0 3 EV-134 AAT4252A EVAL Dual Slew Rate Controlled Load Switch Test: Slew Rate Controlled Turn On Response 1. Configure the specified test equipment as shown in Figure 3 2. Enable channel A and B by a PWM function generator (Note: using the jumper to connect ENA or ENB to INA or INB will force the outputs to follow the inputs). Connect the FAST pin to INA or INB using JP2 or JP3 for FAST turn-on slew rate, and connect it to GND using JP4 for SLOW turn-on slew rate. A. INA and INB in parallel: 1. Use JP1 jumper to connect inputs A and B together, set input voltage to 3.6V (use only one power supply) and output current loads to 1A for each output. 2. Toggle the FAST pin between VIN and GND using JP2, JP3, and JP4 as shown in Figure 3 while observing the FAST and SLOW turn-on and turn-off slew rate from each separate output. 3. Repeat steps 1 and 2 for different output current loads and input voltages. B. INA and INB independently: 1. Remove JP1 to separate INA and INB, set INA to 3.0V and INB to 4.2V, set output current loads to 1A for each output. 2. Toggle the FAST pin between VIN and GND using JP2, JP3, and JP4 as shown in Figure 3 while observing the FAST and SLOW turn-on and turn-off slew rate from each separate output. 3. Repeat steps 1 and 2 for different output current loads and input voltages. 4 EV-134.2007.06.1.0 EV-134 AAT4252A EVAL Dual Slew Rate Controlled Load Switch 4.2V 3.0V Voltmeter Voltmeter Power Supply 3.00V Oscilloscope 1A CURRENT PROBE LOAD 1A Power Supply 4.2V 1A LOAD 1A PWM 100Hz JP3 INB INA INA INB INA JP4 JP2 INB GND GND INA JUMPER 2 FAST = INA = HIGH FAST SLEW RATE JUMPER 3 FAST = INB = HIGH FAST SLEW RATE JUMPER 4 FAST = GND = LOW SLOW SLEW RATE Figure 3: AAT4252A Evaluation Board Connection Diagram for Slew Rate Test. EV-134.2007.06.1.0 5 EV-134 AAT4252A EVAL Dual Slew Rate Controlled Load Switch Test: Enable Behavior 1. 2. 3. 4. Configure the specified test equipment as shown in Figure 4. Disconnect INB to power supply, set INA to designed input voltage, ENA to 0.4V, and FAST to GND (JP4). Connect OUTA through a 100Ω resistor to GND. Ramp up the ENA voltage until OUTA on the oscilloscope flips over (from 0V to VIN) and record ENA voltage at this pin as VIL 5. Ramp down the ENA voltage until OUTA on the oscilloscope flips over (from VIN to 0V) and record ENA voltage at this pin as VIH. The ON/OFF logic low voltage (VIL) and the logic high voltage (VIH) should be within the range from 04 V to 1.4 V. 6. Repeat steps 1 through 5 for channel B. 3.0V Voltmeter Power Supply 3.00V Oscilloscope 1A 100Ω Power Supply 0.5 V 10mA 0.5V Voltmeter JP3 INB INA INA INB INA JP4 JP2 INB GND GND INA JUMPER 2 FAST = INA = HIGH FAST SLEW RATE JUMPER 3 FAST= INB = HIGH FAST SLEW RATE JUMPER 4 FAST = GND = LOW SLOW SLEW RATE Figure 4: AAT4252A Evaluation Board Connection Diagram for Enable Test. 6 EV-134.2007.06.1.0 EV-134 AAT4252A EVAL Dual Slew Rate Controlled Load Switch Test: Output Pull Down Impedance at Shutdown as Shown in Figure 3. 1. Remove JP1 jumper, set INA to 5V, and set ENA and ENB to 0V to disable both channels. 2. Use the second power supply to force 100mA current into the OUTA terminal by setting the power supply output voltage to 1V, and current limit to around 100mA. The voltage at pin OUTA and its sinking current are monitored by a voltmeter and an ammeter. 3. Determine the output pull down impedance of channel A by taking the ratio of OUTA voltage and the sinking current 100mA. 4. Repeat the above steps for channel B output pull down impedance. Power Supply 3.00V 1A 0.923V 100mA Voltmeter Ammeter Power Supply 1V 100mA Figure 5: AAT4252A Evaluation Board Connection Diagram for Output Pull Down Impedance Test. EV-134.2007.06.1.0 7 EV-134 AAT4252A EVAL Dual Slew Rate Controlled Load Switch Printed Circuit Board Figure 6: AAT4252A Evaluation Board Top Layer (not to scale) Figure 7: AAT4252A Evaluation Board Bottom Layer (not to scale) © Advanced Analogic Technologies, Inc. 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