Three-Phase Brushless DC Motor Pre-Driver


Product Image


Top Features


The A4938 is a complete three-phase brushless DC (BLDC) motor pre-driver, supplying direct, high-current gate drive of an all N-channel power MOSFET three-phase bridge. The device has three Hall-element inputs, a sequencer for commutation control, fixed off-time pulse width modulation (PWM) current control, and locked-rotor detection.

Output current is scaled by the capability of the external MOSFETs. Locked rotor detection delay is set by an external capacitor on the CLD terminal. The ENABLE, DIR, and BRAKEZ inputs can be used to control motor speed, position, and torque. Motor speed can be determined using the FG1 output.

The external MOSFETS can be PWMed using an external signal on the PWM input, or using the internal PWM current regulator. In either case, the A4938 synchronous rectification feature reduces power dissipation by turning on the appropriate MOSFETs during current decay.

The Hall elements can be inexpensive types, when used with noise filtering to prevent false commutation signals. The A4938 provides a regulated 5.0 V supply to power the three Hall elements. Internal circuit protection includes thermal shutdown with hysteresis, undervoltage lockout, and dead time protection. Special power-up sequencing is not required. Operating temperature range is –40°C to 85°C. Allegro recommended hall latches: APS13290-1.

  • Drives 6 N-channel MOSFETs
  • Synchronous rectification for low power dissipation
  • Internal UVLO and thermal shutdown circuitry
  • Hall element inputs
  • PWM current limiting
  • Dead time protection
  • FG outputs
  • Standby mode
  • Lock detect protection
  • Overvoltage protection

The A4938 is supplied in a 5 mm × 5 mm, 28-terminal QFN package with exposed thermal pad (suffix ET). This small footprint package is lead (Pb) free with 100% matte tin leadframe plating.

Part Number Specifications and Availability