3.5A Unipolar Stepper Motor Driver

Compact Unipolar stepper motor driver can drive unipolar motor up to 3.5A and supply range 10 To 50V DC. This compact board is based on STK672-440BN IC from ON semiconductor. The STK672-440BN is a hybrid IC for use as a unipolar, 2-phase stepper motor driver with PWM current control with Micro-stepping.

3.5A Unipolar Stepper Motor Driver

Note: This Board can work with motor supply up to 36V DC, for 50V DC Supply Remove IC U2 LM317, and provide 5V Logic supply from external source. Default Enable pin is High for normal operations, pull down 0 to disable the operations, for internal Power on Reset R7 is 0E , C4 can be omit or its fine as it is.

D1 LED : Excitation Monitor ( Motor Pulse Indicator)

D3 LED : Power LED

D2 LED : Fault Indicator When Over Current, Over Heat, and Motor wires open

CN2 : 1 Pin 5V DC, 2 Pin Direction Put, 3 Pin Clock Input, 4 Pin Enable, 5 Pin Not Connected, 6 Pin Fault 2, 7 Pin GND

CN3 : Stepper Motor Connection

CN 1 : Supply Input ( 10-36V DC) Read Note For Supply 46V Input


  • Supply 36V DC (Up to 50V DC See Note)
  • Load Current 3.5Amps
  • Stepper Motor: 5 Wires, 6 Wires, 8 Wires (Unipolar)
  • Built-in motor terminal open detection function, (output current OFF).
  • Overcurrent detection function, (output current OFF).
  • Overheat detection function (output current OFF).
  • FAULT1 signal (active low) is output when any of motor terminal open, overcurrent or overheat is detected.
  • The FAULT2 signal is used to output the result of activation of protection circuit detection at 3 levels.
  • Built-in power on reset function
  • A micro-step sine wave-driven driver can be activated merely by inputting an external clock.
  • External pins can be used to select 2, 1-2 (including pseudo-micro), W1-2, 2 W1-2, or 4W1-2 excitation.
  • The switch timing of the 4-phase distributor can be switched by setting an external pin (MODE3) to detect either the rise or fall, or rise only, of CLOCK input.
  • Phase is maintained even when the excitation mode is switched.
  • Incorporating a current detection resistor (0.122Ω: resistor tolerance 2%),
  • Motor current can be set using Trimmer Potentiometer ( V Ref Range 0.2V-1.8V)
  • The ENABLE pin can be used to cut output current while maintaining the excitation mode
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