Automotive Full Bridge MOSFET Driver

The A3921 is a full-bridge controller for use with external N-channel power MOSFETs and is specifically designed for automotive applications with high-power inductive loads, such as brush DC motors.

A unique charge pump regulator provides full (>10 V) gate drive for battery voltages down to 7  V and allows the A3921 to operate with a reduced gate drive, down to 5.5 V. A bootstrap capacitor is used to provide the above-battery supply voltage required for N-channel MOSFETs. An internal charge pump for the high-side drive allows DC (100% duty cycle) operation.

The full bridge can be driven in fast or slow decay modes using diode or synchronous rectification. In the slow decay mode, current recirculation can be through the high-side or the lowside FETs. The power FETs are protected from shoot-through by resistor adjustable dead time.

Integrated diagnostics provide indication of undervoltage, overtemperature, and power bridge faults, and can be configured to protect the power MOSFETs under most short circuit conditions.

The A3921 is supplied in a 28-pin TSSOP power package with an exposed thermal pad (suffix LP). This package is lead (Pb) free, with 100% matte tin leadframe plating.