Three-Phase Power MOSFET Controller


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The A3938 is a three-phase, brushless DC motor controller. It has a high-current gate drive capability that allows driving of a wide range of power MOSFETs and can support motor supply voltages to 50 V. The A3938 integrates a bootstrapped high-side driver to minimize the external component count required to drive N-channel MOSFET drivers.

Internal fixed off-time, PWM current-control circuitry can be used to regulate the maximum load current to a desired value. The peak load current limit is set by the user’s selection of an input reference voltage and external sensing resistor. A userselected external RC timing network sets the fixed off-time pulse duration. For added flexibility, the PWM input can provide speed/torque control where the internal current control circuit sets a limit on the maximum current.

The A3938 includes a synchronous rectification feature. This shorts out the current path through the power MOSFET reverse body diodes during PWM off-cycle current decay. This can minimize power dissipation in the MOSFETs, eliminate the need for external power clamp diodes, and potentially allow a more economical choice for the MOSFET drivers.

The A3938 provides commutation logic for Hall sensor ICs configured for 120-degree spacing. The Hall input pins are pulled up to an internally-generated 5 V reference. Power MOSFET protection features include: bootstrap capacitor charging current monitor, regulator undervoltage monitor, motor lead short-to-ground, and thermal shutdown. Allegro recommended hall latches: APS13290-1.

  • Drives a wide range of N-channel MOSFETs
  • Low-side synchronous rectification
  • Power MOSFET protection
  • Adjustable dead time for cross-conduction protection
  • Selectable coast or dynamic brake on power-down or RESET input
  • Fast/slow current decay modes
  • Internal PWM current control
  • Motor lead short-to-ground protection
  • Internal 5 V regulator
  • Fault diagnostic output
  • Thermal shutdown
  • Undervoltage protection

The 38-Pin LD package is lead (Pb) free, with 100% matte tin plated leadframe.


Part Number Specifications and Availability