DEMO MANUAL DC2543B LTC7820EUFD High Efficiency, Charge Pump DC/DC Converter DESCRIPTION Demonstration circuit 2543B is a high efficiency, high The DC2543B needs to be powered on with no load cur- density, open loop charge pump (inductorless) DC/DC rent or a very small load current (less than 50mA) with converter. This demo board is a voltage divider which the default setup. Large load current can be applied after achieves a 2:1 step-down ratio from an input voltage from V is established. The board offers a disconnect FET O 36V to 60V. The output voltage is a fixed ratio of half of the option which is controlled by the LTC7820 FAULT pin input voltage (V /2) and can supply a 10A load current. to disconnect the load during startup as shown in the IN This demo board has the option to deliver a 20A maximum schematic. Please refer to Voltage Divider Prebalance load with the addition of 15 chip capacitors. See Figure8 Before Switching section in the LTC7820 data sheet for and Figure10 for the details. more details regarding the startup of the voltage divider. The board also features some protection functions The DC2543B provides a very high efficiency solution of such as overcurrent and thermal shutdown to make it a 98.7% when converting 48V to 24V at 10A as shown IN OUT reliablesolution. in Figure3. When configured for a 20A output, an effi- ciency of up to 98.4% is achievable for a 48V to 24V Design files for this circuit board are available. IN OUT at 20A as shown in Figure8. All registered trademarks and trademarks are the property of their respective owners. The demo board features the LTC 7820, a fixed ratio high voltage high power switched capacitor/charge pump controller in a 4mm 5mm QFN package. Please see LTC7820 data sheet for more detailed information. PERFORMANCE SUMMARY Specifications are at T = 25C A PARAMETER CONDITION VALUE Input Voltage Range 36V to 60V Output Voltage, V V = 36 to 60V, I = 0A to 10A V /2 OUT IN OUT IN Maximum Output Current, I V = 36 to 60V, V = V /2 10A OUT IN OUT IN Typical Efficiency V = 48V, V = 24V, I = 10A 98.7% IN OUT OUT Peak Efficiency V = 48V, V = 24V 99% IN OUT Switching Frequency 200kHz NOTE: DC2543B demo board includes a Schottky diode added across the output. This manual describes the demo board entitled Demo Circuit 2543B. The DC2543B replaces the DC2543A. Rev. 0 1DEMO MANUAL DC2543B QUICK START PROCEDURE Demonstration circuit 2543B is easy to set up to evaluate Notes: the performance of the LTC7820. Refer to Figure1 for 1. When measuring the output or input voltage ripple, the proper measurement equipment setup and follow the do not use the long ground lead on the oscilloscope procedure below. probe. See Figure3 for the proper scope probe tech- 1. With power off, connect the input power supply to V nique. Short, stiff leads need to be soldered to the (+) IN (36V to 60V) and GND (input return). and () terminals of an output capacitor. The probes ground ring needs to touch the () lead and the probe 2. Connect the output loads between V and GND OUT tip needs to touch the (+) lead. (Initial load: no load). Refer to Figure1. 2. When doing the load step test with the on-board 3. Connect the DVMs to the input and output. dynamic load circuit, please make sure the load step- 4. Check the default jumper/switch position: SW1 (RUN): up pulse duty cycle does not exceed 2% and the pulse OFF JP2 (BIAS): ON. duration is less than 500s so that the temperature of the MOSFETs Q9, Q23 in the dynamic load circuit 5. Turn on the input power supply and adjust voltage stay in the safe region. Instead of using the on-board to48V. dynamic load circuit, an electric load can also be used NOTE: Make sure that the input voltage does not for the load step test, which does not have the 2% exceed60V. maximum duty cycle limit for the load step. 6. Turn on the switches: SW1: ON. 3. It is recommended to set the electronic load in CR (con- + stant resistance) mode for evaluation of the DC2543B 7. Check for the proper output voltages from V to O SNS board. Some electronic loads draw negative current in V . O SNS CC (constant current) mode when evaluating the output 8. Once the proper output voltage is established, adjust overcurrent protection feature of DC2543B, which can the loads within the operating range and measure the violate the absolute maximum voltage rating 0.3V for efficiency, output ripple voltage and other parameters. V pin. LOW 9. After completing all tests, adjust the load to 0A, power off the input power supply. Rev. 0 2