A3935: Three-Phase Power MOSFET Controller


A3935KLQTR-T variant is in production but has been determined to be NOT FOR NEW DESIGN. This classification indicates that sale of the variant is currently restricted to existing customer applications. The variant should not be purchased for new design applications because obsolescence in the near future is probable. Samples are no longer available. Status change: October 31, 2011. Recommended Replacement: A4933KJPTR-T.

A3935KLQTR variant has been determined to be obsolete and is no longer in production. Status change: October 31, 2011.

The A3935 is designed specifically for automotive applications that require high-power motors. Each provides six high-current gate drive outputs capable of driving a wide range of N-channel power MOSFETs.

A requirement of automotive systems is steady operation over a varying battery input range. The A3935 integrates a pulse-frequency modulated boost converter to create a constant supply voltage for driving the external MOSFETs. Bootstrap capacitors are utilized to provide the above battery supply voltage required for N-channel FETs.

Direct control of each gate output is possible via six TTL-compatible inputs. A differential amplifier is integrated to allow accurate measurement of the current in the three-phase bridge.

Diagnostic outputs can be continuously monitored to protect the driver from short-to-battery, short-to-supply, bridge-open, and battery under/overvoltage conditions. Additional protection features include dead-time, VDD undervoltage, and thermal shutdown.

Top Features

  • Drives wide range of N-channel MOSFETs in 3-phase bridges
  • PFM boost converter for use with low-voltage battery supplies
  • Internal LDO regulator for gate-driver supply
  • Bootstrap circuits for high-side gate drivers
  • Current monitor output
  • Adjustable battery overvoltage detection
  • Diagnostic outputs
  • Motor lead short-to-battery, short-to-ground, and bridge-open protection
  • Undervoltage protection
  • –40°C to 150°C TJ operation
  • Thermal shutdown

Part Number Specifications and Availability

Part Number Package Type Temperature RoHS
Part Composition /
RoHS Data
Comments Samples Check Stock
A3935KLQTR 36-lead QSOP -40°C to 135°C Yes View Data Discontinued Contact your
local sales rep
Distributor Stock
A3935KLQTR-T 36-lead QSOP -40°C to 135°C Yes View Data Not for new design 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 A3935 is supplied in a 36-lead 0.8 mm pitch QSOP (package LQ, similar to SOICW).  The lead (Pb) free variants (suffix –T ) have 100% matte tin leadframe plating.