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) and can supply a 10A load current. 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 of 98.7% when converting 48VIN to 24VOUT at 10A. When configured for a 20A output, an efficiency of up to 98.4% is achievable for a 48VIN to 24VOUT at 20A. The demo board features the LTC7820, 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. 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.

Supervisory Circuits Cascadable Super Sequencer w/ Margin con

The LTC1625 is a synchronous step-down switching regulator controller that drives external N-Channel power MOSFETs using few external components. Current mode control with MOSFET VDS sensing eliminates the need for a sense resistor and improves efficiency. The frequency of a nominal 150kHz internal oscillator can be synchronized to an external clock over a 1.5:1 frequency range.Burst Mode? operation at low load currents reduces switching losses and low dropout operation extends operating time in battery-powered systems. A forced continuous mode control pin can assist secondary winding regulation by disabling Burst Mode operation when the main output is lightly loaded.Fault protection is provided by foldback current limiting and an output overvoltage comparator. An external capacitor attached to the RUN/SS pin provides soft start capability for supply sequencing. A wide supply range allows operation from 3.7V (3.9V for LTC1625I) to 36V at the input and 1.19V to VIN at the output.Applications Notebook and Palmtop Computers, PDAs Cellular Telephones and Wireless Modems Battery Chargers Distributed Power

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