A3938: 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
LD-TSSOP 38 pin

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


Part Number Specifications and Availability

Part Number Package Type Temperature RoHS
Part Composition /
RoHS Data
Comments Samples Check Stock
A3938SLDTR-T 38-lead TSSOP -20°C to 85°C Yes View Data Contact your
local sales rep
Distributor Stock

Allegro’s products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of Allegro’s product can reasonably be expected to cause bodily harm.