DEMO MANUAL DC2041A LTC3255EMSE Wide V Range Fault Protected IN 50mA Step-Down Charge Pump Description Demonstration circuit 2041A is a switched-capacitor The LTC3255 is a robust device that can survive reverse- step-down power supply featuring the LTC 3255. The polarity input supplies with current limit and overtem- LTC3255 has the ability to step down voltage 2:1 to ef- perature protection. ficiently regulate output voltages less than half the V IN Refer to the LTC3255 data sheet for more details on the voltage reducing the input current needed. As V reduces IN electrical and timing specifications. below twice V , the LTC3255 will automatically switch OUT Design files for this circuit board are available at to 1:1 mode. DEMO MANUAL DC2041A Quick s Dp The DC2041 is easy to set up to evaluate the performance 4. With power off, connect a 0V to 48V, 100mA power of the LTC3255 with the shunt disabled. Refer to Figure 1 supply to V and GND with a voltmeter as shown in IN for proper measurement equipment setup with the shunt Figure 1. disabled and follow the evaluation procedure below. To 5. Turn on the V input power supply and increase the IN evaluate the LTC3255 with the shunt enabled, go to the supply until the V voltage is in regulation and the OUT SHUNT ENABLED section. PGOOD voltage is pulled to V . OUT NOTE. When measuring the input or output voltage ripple, NOTE. Make sure that the input voltages do not exceed 60V. care must be taken to avoid a long ground lead on the 6. With V at least 1V above V , increase the load on oscilloscope probe. Measure the input or output voltage IN OUT V from 0mA to 50mA and observe the input current. ripple by touching the probe tip directly across the V or OUT IN The output ripple may also be observed using an oscil- V and GND terminals. See Figure 2 for proper scope OUT loscope with the probe connected as shown in Figure 2. probe technique. 7. With a 50mA load on V , increase V until the cur- 1. Set the EN jumper, JP1, on the DC2041 board to the OUT IN rent on V drops to approximately the V current. ON position. IN OUT 8. Refer to the LTC3255 data sheet for more details on 2. Set the SHUNT jumper, JP3, to the OFF position. how the LTC3255 operates. 3. Set the V jumper, JP2, to the desired output voltage. OUT 9. When done, turn off all loads and power supplies. NOTE. Do not set the V jumper to the OPT setting un- OUT less the appropriate resistor is installed in R7. The V OUT jumper OPT position is to allow an alternate V setting. OUT This can be accomplished by adding a resistor to R7 to set the output to a desired voltage. Refer to the LTC3255 data sheet to calculate the appropriate value for R7. dc2041af 2 ure roce tart