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DRV8701: DRV8701PRGET

Jean Orhan
Prodigy 250 points
Part Number: DRV8701


Dear Sir or Madam,

I would like to ask for some guidance on an issue Im having with a motor control design using the DRV8701PRGET device. I have tested this driving a resistive load, powered by 26V d.c and the H bridge FETs switching a rectified 17V a.c. It works really well for about 30minutes to 45 minutes and current control is present (0 to 16A but after a while it seems to lose the current control and goes to maximum output (16A). FETs are cool but the DRV8701PRGET seems to be getting hot. Can someone please advise what might be wrong and where to start looking?"

Regards,

Jean

  • 0
    TI__Guru** 114905 points
    Hi Jean,

    How are you controlling the current?
    Can you provide some scope captures of the inputs and currents?
  • 0 in reply to Rick Duncan
    Prodigy 250 points

    Hi Duncan,

    Im controlling the power output level with a pot connected to the MCU (called CURRENT). Basically this is a copy of the DRV8701 dev kit. I have attached the schematics of the MCU, regulators and amplifier interface. I will send you scope captures shortly. In the meantime I have noticed the nFAULT output of the amplifier toggling on every zero crossing detection and Im not sure why. I will get you more diagnostic information ASAP.

    Regards,

    Jean

  • 0 in reply to Jean Orhan
    TI__Guru** 114905 points
    Hi Jean,

    Have you compared the nFAULT behavior using Table 7 (Fault Response) of the datasheet? This may provide some clues to the cause.

    What is the value of C16?
  • 0 in reply to Rick Duncan
    Prodigy 250 points

    Hi Rick,

    I have looked at the fault table and it might be that perhaps because the FET output stage is seeing rectified a.c voltage waves its going under-voltage? Im not sure. I will get you the scope shots today so you can see the input voltage, output voltage and various control signals. The value of C16 is 1uF.

    Regards,

    Jean