Worcester, Mass. - Allegro Micro-Systems Inc.'s half-bridge pre-driver IC, the A3946, is designed to drive brush dc motors, three-phase brushless dc motors, switched-reluctance motors and other large inductive loads. Features include fault reporting, extended operating voltages of 7 V to 60 V and extended temperatures (-40 degrees C to +135 degrees C).
The A3946 provides two high-current gate drive outputs that can drive n-channel MOSFETs. The outputs are configured to drive a classic half-bridge. An externally supplied PWM signal to the input of the A3946 switches the high-side gate driver output. The low-side gate driver output can be configured to automatically switch on during the PWM off-time, thereby acting as a synchronous rectifier.
The two inputs are flexible, Allegro said. They either can be tied together to allow for one PWM input signal or they can be driven independently to provide direct control over the high-side and low-side gate drive outputs. In the single PWM input mode, the cross-conduction dead time is determined by the value of an external resistor. When driving the two inputs independently, the system controller determines the cross-conduction dead time.
A bootstrap capacitor provides the above-battery supply voltage required for n-channel MOSFETs. An internal charge pump for the high side will allow for dc operation of the half-bridge.
The A3946 is made using Allegro's ABCD3 (Allegro Bipolar CMOS DMOS third-generation) process and is supplied in a batwing 16-lead SOIC. This half-bridge pre-driver IC is targeted at automotive and industrial markets. The A3946 has a 10- to 12-week lead time-to-market and is priced at 85 cents per part in quantities of 1,000.
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