The Allegro MicroSystems A4952 and A4953 are full-bridge DMOS PWM motor drivers designed for brush DC motor applications in office automation equipment — printers, copiers, and scanners — as well as general industrial DC motor control. Both devices deliver up to 2 A continuous output current from an 8–40 V supply and integrate comprehensive protection features including overcurrent, undervoltage lockout, crossover-current prevention, and thermal shutdown. Synchronous rectification in the DMOS output stage reduces power dissipation during PWM operation, eliminating the need for external Schottky diodes.

What is the difference between the A4952 and A4953?

The two variants share an identical DMOS output stage but differ in fault handling and package. The A4952 (10-pin MSOP) provides an open-drain FLTn fault flag output that asserts low on overcurrent, UVLO, or thermal shutdown, plus a RTRY pin that lets you select between automatic retry after a 2 ms timeout or latched fault behavior. The A4953 (8-pin SOICN) omits both pins — overcurrent faults latch the output until the device enters standby mode or power is cycled — offering a simpler, smaller-footprint option where external fault monitoring is not required.

How does the adjustable current limit work?

Both devices regulate peak motor current via an external sense resistor (RS) on the LSS pin and a reference voltage (VREF). The trip current follows I_TRIP = VREF / (A_V × RS), where A_V is approximately 10 V/V. An internal fixed off-time PWM scheme (typically 25 μs) controls current ripple once the limit is reached. This architecture lets you set the maximum motor current with two external passive components — no microcontroller PWM overhead required — while the 3 μs blank time prevents false triggering during switching transitions.