40_V_INPUT_5_C_10_A_DC_TO_DC_CONVERTER

Published:2009/7/13 2:23:00 Author:May | From:SeekIC

Generating 5 V at 10 A from a 40-V supply with up to 90 percent efficiency is possible using a synchronous switching regulator. The synchronous switching regulator circuit shown achieves this high efficiency by using external MOSFETs with low RDS(ON) and by shunting the Schottky diode after the topside MOSFET has completely turned off to minimize the Schottky diode's conduction losses. The LT1160 half-bridge driver alternately drives the high side and low side MOSFETs ON and OFF during switching. The loop is controlled by the LT3846 current-mode PWM controller and operates at 40 kHz. A key feature of this circuit is the ability to drive the external high-current MOSFETs safely. Internal logic in the LT1160 prevents both MOSFETs from being on at the same time, and its unique adaptive protection against shoot-through currents eliminates all matching requirements for the external MOSFETs. These protection features, in combination with the LT1160's ability to drive up to 10,000 pF of gate capacitance, make paralleling power MOSFETs for high-current applications an easy task. The high-side gate voltage is provided by a floating supply, which is boosted above the HV rail by bootstrap capacitance Cboost. An undervoltage detector in the LT1160 can sense an undervoltage condition at either the input supply or the floating supply and turn off both MOSFETs to prevent excessive power dissipation.



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