Microstepping Programmable Stepper Motor Driver with Stall Detect and Short Circuit Protection


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The A4979 is a flexible microstepping motor driver with built-in translator for easy operation. It is a single-chip solution, designed to operate bipolar stepper motors in full-, half-, quarter- and sixteenth-step modes, at up to 50 V and 1.5 A. The A4979 can be controlled by simple Step and Direction inputs, or through the SPI-compatible serial interface that also can be used to program many of the integrated features and to read diagnostic information.

The current regulator can be programmed to operate in fixed off-time or fixed frequency PWM, with several decay modes to reduce audible motor noise and increase step accuracy. In addition the phase current tables can be programmed via the serial interface to create unique microstep current profiles to further improve motor performance for specific applications.

The current in each phase of the motor is controlled through a DMOS full bridge, using synchronous rectification to improve power dissipation. Internal circuits and timers prevent crossconduction and shoot-through, when switching between highside and low-side drives.

The outputs are protected from short circuits, and features for low load current and stalled rotor detection are included. Chip-level protection includes: hot and cold thermal warnings, overtemperature shutdown, and undervoltage lockout. The A4979 is supplied in a 28-pin TSSOP power package with an exposed thermal pad (package type LP). This package is lead (Pb) free with 100% matte tin leadframe plating.

  • Typical application up to 1.5 A, 50 V
  • Stall detect features
  • Low RDS(on) outputs, 0.5 Ω source and sink, typical
  • Automatic current decay mode detection/selection
  • Mixed, Fast, and Slow current decay modes
  • Synchronous rectification for low power dissipation
  • Internal UVLO and Thermal Shutdown circuitry
  • Crossover-current protection
  • Short circuit and open load diagnostics
  • Hot and cold thermal warning
  • SPI-compatible or simple Step and Direction motion control
  • Highly configurable via SPI-compatible serial interface
28-pin TSSOP with exposed thermal pad (suffix LP)

Part Number Specifications and Availability