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DRV8832: Output voltage behaviour not right

Daniel_U
Prodigy 235 points
Part Number: DRV8832
Other Parts Discussed in Thread: DRV8830, DRV8837

Hello,

I am using the DRV8832 in a minimal setup with ISENSE pulled low and VREF connected to VSET to disable current limit and drive the motor at maximum voltage. VCC is 5V decoupled with 2 x 0.1µF capacitors.

IN1 is pulled high and on IN2 applied is a PWM signal with 50% duty-cycle and 100Hz (red). The output voltage on OUT2 (yellow) looks like this (2V / 5ms):

Normally a 44.5 kHz output-signal would be expected but there is clearly something wrong.

Can anyone help me with this problem?

Regards

Daniel

  • 0
    TI__Guru** 114905 points
    Hi Daniel,

    Please refer to the Bridge Control Section of the datasheet:

    Note that when transitioning from either brake or sleep mode to forward or reverse, the voltage control PWM starts at zero duty cycle. The duty cycle slowly ramps up to the commanded voltage. This can take up to 12 ms to go from sleep to 100% duty cycle. Because of this, highspeed PWM signals cannot be applied to the IN1 and IN2 pins. To control motor speed, use the VSET pin as described below.

    It appears that the output duty cycle is increasing when IN2 is low, but does not reach 100% duty cycle and enters brake mode.

    If you want to run the motor at maximum voltage, connect VSET to VREF and set IN2 low with IN1 high. The device will ramp the duty cycle until 100% is reached.
  • 0 in reply to Rick Duncan
    Prodigy 235 points
    Hello Rick,

    so this means that I can only control the motor speed via the VSET pin and IN1/IN2 can only serve for controlling the direction?
    If true, is there any other product like this but where the speed can be controlled via PWM and the device then holds this speed under different VCC voltage levels? I only know the DRV8830 with I2C but the steps between voltage levels are too big for me.

    Thanks
    Daniel
  • 0 in reply to Daniel_U
    TI__Guru** 114905 points
    Hi Daniel,

    You have located the two devices (DRV8832 and DRV8830) that contain this control.
    But the speed control feature has been disabled when connecting VREF to VSET.

    Any of the IN1/IN2 devices like the DRV8837 can control the speed by adjusting the duty cycle. An example of how to do this can be found here:

    e2e.ti.com/.../easy-cruise-control-for-brushed-motors-using-bemf