A5985: DMOS Microstepping Driver with Translator and Overcurrent Protection



Top Features

The A5985 is a complete microstepping motor driver with built-in translator for easy operation. It is designed to operate bipolar stepper motors from full-step up to 1/32 step modes. Step modes are selectable by MSx logic inputs. It has an output drive capacity of up to 40 V and ±2 A.

A5985 introduces a proprietary QuietStepTM algorithm to optimize the current waveform over a wide range of stepper speeds and stepper motor characteristics. QuietStepTM adjusts on-the-fly the amount of fast decay during a PWM cycle to keep current ripple at a low level over the various operating conditions. This adaptive feature improves performance of the system resulting in reduced audible motor noise, reduced vibration, and increased step accuracy.

The translator is the key to the easy implementation of the A5985. Simply inputting one pulse on the STEP input drives the motor one microstep. There are no phase sequence tables, high frequency control lines, or complex interfaces to program. The A5985 interface is an ideal fit for applications where a complex microprocessor is unavailable or is overburdened.

Internal synchronous rectification control circuitry is provided to improve power dissipation during PWM operation. Internal circuit protection includes: thermal shutdown with hysteresis, undervoltage lockout (UVLO), and crossover-current protection. Special power-on sequencing is not required.

The A5985 is supplied in a surface-mount QFN package (ET), 5 mm × 5 mm, with a nominal overall package height of 0.90 mm and an exposed pad for enhanced thermal dissipation. It is lead (Pb) free (suffix –T), with 100% matte tin-plated leadframes.

  • Drop-in replacement for A4988
  • Proprietary QuietStep option
  • Low RDS(on) outputs
  • Single supply
  • Microstepping up to 32 microsteps per full step
  • Full torque step modes
  • Short-to-ground protection
  • Shorted load protection
  • Short-to-battery protection
  • Fault output
  • Low current Sleep mode, < 10 μA
  • Thin profile QFN
  • Thermal shutdown circuitry
  • Synchronous rectification for low power dissipation
  • Internal UVLO
  • Crossover-current protection

Part Number Specifications and Availability

Part Number Package Type Temperature RoHS
Part Composition /
RoHS Data
Comments Samples Check Stock
A5985GETTR-T 28-lead QFN -40°C to 105°C Yes View Data Contact your
local sales rep
Distributor Stock
APEK5985GET-01-T DEMO BOARD -40°C to 105°C No -- 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.



Design Support Tools

A5985 Demo Board Schematic