DMOS microstepping driver uses proprietary control method for accuracy

Proprietary current control is claimed to maximise microstepping accuracy in the new, integrated bipolar stepper motor driver IC from Allegro Microsystems Europe. The A5985 motor driver IC has a built-in translator for easy operation and is designed to operate bipolar stepper motors from full-step up to 1/32 step modes that are selectable by MSx logic inputs.

Output drive capacity is up to 40V and ±2A. The driver operates with a single supply.  It is targeted at the office and industrial automation markets, such as automatic teller machines, point of sale and laser printers, 3D printers, robotics, vending, copiers, CCTV cameras and sewing machines.

The IC introduces a proprietary Adaptive Percent Fast Decay (APFD) algorithm to optimise the current waveform over a wide range of stepper speeds and stepper motor characteristics.  APFD adjusts, on-the-fly, the amount of fast decay to maintain current regulation while minimising current ripple. This adaptive feature improves performance of the system, says the company, reducing audible motor noise, vibration, and increasing step accuracy.

The translator inputs one pulse on the step input to drive the motor one microstep. There are no phase sequence tables, high frequency control lines, or complex interfaces to program.

Internal synchronous rectification control circuitry improves power dissipation during PWM operation, says the company. Internal circuit protection includes over-current protection for motor lead short to ground or supply, thermal shutdown with hysteresis, under-voltage lockout (UVLO), and crossover-current protection. Special power-on sequencing is not required.

The device is supplied in a 28pin, 5.0 x 5.0 x 0.9mm QFN package (ET designator) with exposed pad for enhanced thermal dissipation, The package is lead-free, with 100% matt tin plated leadframe.


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