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Dual full-bridge gate driver reduces system vibration

Posted: 14 Sep 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Allegro MicroSystems? A3986? dual full-bridge? gate driver?

Allegro MicroSystems Inc. has released a dual full-bridge gate driver with integrated micro stepping translator suitable for driving medium to high-power bipolar two-phase stepper motors. The company said its A3986 meets the market need for a low-cost stepper motor driver that exceeds the output current range of existing fully integrated IC solutions limited to 2A to 3A.

Full step to sixteenth step micro stepping control promises to reduce system vibration and improve overall positioning accuracy. The device targets the industrial and office automation markets.

Motor power is provided by external N-channel power MOSFETs at supply voltages of 12-50V. The new device provides the necessary circuitry to ensure that the gate-source voltage of both high-side and low-side external MOSFETs are above 10V and that the gate capacitance is quickly charged and discharged in order to reduce power dissipation during switching, Allegro explained.

This device contains two sinusoidal DACs that generate the reference voltage for two fixed-off-time PWM current controllers, which provide current regulation for external power MOSFET full-bridges. These PWM regulators automatically switch between slow and fast or mixed decay modes. This patented current decay scheme results in reduced audible noise, increased step accuracy and lower power dissipation.

Using synchronous rectification enhances efficiency and the external power MOSFETs are protected from shoot-through by integrated crossover control and programmable dead time.

The A3986 is supplied in a Pb-free 38-pin TSSOP package with 100 percent matte tin leadframe plating.

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