DC2543B: 20A, 36 ~ 60V in, 2:1 Step-Down Charge Pump

Demonstration circuit 2543B is a high efficiency, high density, open loop charge pump (inductorless) DC/DC converter. This demo board is a voltage divider which achieves a 2:1 step-down ratio from an input voltage from 36V to 60V. The output voltage is a fixed ratio of half of the input voltage (VIN/2). This demo board has the option to deliver a 20A maximum load with the addition of 15 chip capacitors.

The DC2543B provides a very high efficiency solution. When configured for a 20A output, an efficiency of up to 98.4% is achievable for a 48VIN to 24VOUT at 20A.

The DC2543B needs to be powered on with no load current or a very small load current (less than 50mA) with the default setup. Large load current can be applied after VO is established. The board offers a disconnect FET option which is controlled by the LTC7820 FAULT pin to disconnect the load during startup as shown in the schematic. Please refer to “Voltage Divider Prebalance Before Switching” section in the LTC7820 data sheet for more details regarding the startup of the voltage divider. The board also features some protection functions such as overcurrent and thermal shutdown to make it a reliable solution.

The demo board features the LTC7820, a fixed ratio high voltage high power switched capacitor/charge pump controller in a 4mm × 5mm QFN package. The LTC®7820 is a fixed ratio high voltage high power switched capacitor/charge pump controller. The device includes four N-channel MOSFET gate drivers to drive external power MOSFETs in voltage divider, doubler or inverter configurations. The device achieves a 2:1 stepdown ratio from an input voltage as high as 72V, a 1:2 step-up ratio from an input voltage as high as 36V, or a 1:1 inverting ratio from an input voltage up to 36V. Each power MOSFET is switched with 50% duty cycle at a constant pre-programmed switching frequency. System efficiency can be optimized to over 99%. The LTC7820 provides a small and cost effective solution for high power, non-isolated intermediate bus applications with fault protection.