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DRV8840 VCP

user4312303
Prodigy 10 points
Other Parts Discussed in Thread: DRV8840

I have a few questions regarding the DRV8840:

- Can anyone give me an idea what voltages to expect at the VCP pin? Why is the 1M reqsistor on that pin necessary? It is not implemented in the EVM.

- Would you decouple the VM pins? Or is this not necessary as they are just the motor power connections. Is bulk capacitance necessary or only 100n?

Thanks in advance!

  • 0
    TI__Mastermind 26065 points
    Hi

    Normally you will see about VM + 10~12V in VCP pin when the device is not in SLEEP.
    We recommended 1M for VCP because this helps to discharge the VCP cap after the power off. Otherwise, sometime the device will still have the internal high side MOSFETs partly ON after power off and causing a braking effect to the motor that you can hardly move the motor by external force.

    Decouple the VM pin is the most important thing of design the circuit and PCB. We should always keep a bulk cap >100uF and a 0.1uF closely placed by the VM pins to GND plane. Only 0.1uF is not enough of course.

    Best regards,