TA7289 stepper motor microstep driver circuit

The maximum power supply voltage of this circuit is 30V. The output phase current peak value is 1.5A, and the continuous
current is 0 7A. The signal input terminal is TTL level compatible.
  As can be seen from the schematic block diagram, its main internal components are: oscillator <osc),
4-bit D/A converter, PWM comparator, logic gate circuit, and H-bridge power switch.
  It is a bipolar drive circuit . The size and polarity of the winding current depend on
  the reference voltage VREF input from pin 1 and the 4-bit data input from pins 11-14. The current flowing through the winding
  flows through the external current detection resistor Rs connected to pin 7, resulting in a voltage drop
  . After the noise is removed by the RF and CF low-pass filters, it is input from pin 5 to the inverting input end of the PWM comparator. The current command signal from
  the D/A converter is sent to the non-inverting input terminal of the comparator, and the sawtooth signal from the oscillator is also
  input . The PWM signal obtained from the comparator
  is used to modulate the output of the H-bridge, so that the winding current changes with the change of the current command,
  thereby achieving chopping control of the current.