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DRV8412: The output is absent

Part Number: DRV8412

Hi to all, I'm using this driver to drive a DC motor.

I shorted to gorund M!, M2 and M3. I powered the IC with +12Vdc and I provided a complementary PWM at the input (PWM_A and PWM_B) but the OUT_A and OUT_B are also 0V.

I checked that the RESET pin are high and there are no fault.

What an I wrong?

  • Hi Serafino,

    What is the voltage on the other pins?
    VREG
    VDD
    GVDD_x
    What is the OC_ADJ resistor?

    Are the outputs loaded?
    How are you measuring the outputs (with a scope or with a DMM)?
    Assuming you are using a DMM, please try using a scope.
  • VREG = 3.39V
    VDD = 12.3V
    GVDD_x = 12.3V
    What is the OC_ADJ resistor = 82k

  • I measured with a scope in both conditions: with and without load

  • Here below the electrical scheme I'm using

  • Hi Serafino,

    What is the PWM frequency and duty cycle?
    What is your bulk capacitor value on the +12V signal? I see each output with a 47uF capacitor to ground but do not see much bulk capacitance.
    Can you add a 1k/1k resistor divider from PVDD to GND with the center connection at OUTA? This can help determine if the outputs are really driving to 0, or disabled?
    Can you provide a scope capture of PWM_A and OUTA?
    If the outputs are disabled, please remove the 47uF and 470nF capacitors on OUT_X1+ and OUT_X1- and try again.
  • Hi Rick, the frequency is 7.37kHz and the duty cycle is 50%.

    The bulk capacitor on +12Vdc is 100uF

    With and without the partitor the situation is the same. But if I remove the capacitor after the inductors, I can see the waveform.

    I would say that I'm using this capacitor value since I see this in the development board  of the DRV8412.

    So my question is: should I use some capacitor at the output or not?

    The use of series inductor is necessary or also this could be removed?

    Thank you for your support

  • Hi Serafino,

    You should have seen the waveform if you zoomed in to a 10us/div. The 100nF bootstrap capacitor is intended to be used at frequencies higher than 10kHz. If you planning to run a lower PWM frequency, the bootstrap capacitor should be increased and a 5 Ohm series resistors should be added between the GVDD supply and the GVDD_x pins as described in section 7.3.2.1 of the datasheet.

    The development board is intended to demonstrate several applications such as brushed motor, stepper motor, and thermo electric cooling (TEC).

    Are you planning to control a TEC? If not, the capacitors are not required.
    The series inductors are recommended to protect against a short. Please refer to the 6th paragraph in section 7.3.2.2 of the datasheet for more details.
  • Hi Rick,

    during the last days I was working with the driver. But the driver after 30mins that it works well, the ouptu is yet absent. I noted that only one output over two is not working. It is constant to zero even if the pwm inputs are correct and present.

    No fault or otw warning are present.

    Do you have any suggestions?

  • Hi Serafino,

    Does the device recover after a power cycle or toggling the RESET pins?

    If the device recovers, you may be hitting the cycle by cycle limit. To recover, the PWM input pair must be cycled.

    From section 7.4 of the datasheet:
    In operation modes 1, 2, and 4 (CBC current limit is used), once the CBC current limit is hit, the driver will be
    deactivated until the next PWM cycle starts. However, in order for the output to be recovered, the PWM input
    corresponding to that driver in CBC must be toggled. Because of this, CBC mode does not support operation
    when one half-bridge PWM input is tied to dc logic level.
  • Each motor is sinked about 0.6A. This value is closed to the CBC limit.
    When I send a reset pulse,sometimes the driver restarts, sometimes no.
    Please, how can I fix my problem?