A4934: Three-Phase Sensorless Fan Driver


This device is no longer in production. The device should not be purchased for new design applications. Samples are no longer available. Date of status change: October 31, 2011.

Recommended Substitutions: For existing customer transition, and for new customers or new applications, refer to the A4941.

The A4934 three-phase motor driver incorporates BEMF sensing to eliminate the requirement for Hall sensors in fan applications.

A pulse wave modulated (PWM) input is provided to control motor speed, allowing system cost savings by eliminating external variable power supply. PWM input can also be used as an on/off switch to disable motor operation and place the IC into a low power standby mode.

The A4934 soft switching settings are designed for lower inductance or lower speed motors. For higher inductance or higher speed motors consider using the pin-compatible A4941.

Top Features

  • Sensorless (no Hall sensors required)
  • Soft switching for reduced audible noise
  • Minimal external components
  • PWM speed input
  • FG speed output
  • Low power standby mode
  • Lock detection
  • Optional overcurrent protection

Part Number Specifications and Availability

Part Number Package Type Temperature RoHS
Part Composition /
RoHS Data
Comments Samples Check Stock
A4934GLPTR-T 16-lead TSSOP -40°C to 105°C Yes View Data Discontinued 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.


The A4934 is provided in a 16-pin TSSOP package (suffix LP) with an exposed thermal pad. It is lead (Pb) free, with 100% matte tin leadframe plating.

LP 16-pin TSSOP