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DRV8870: Check the schematic for DRV8870

Mickey Zhang
Genius 12080 points
Part Number: DRV8870

Hi team,

The customer uses DRV8870. The customer's schematic is in the attach. 

ISEN pin is shorted to GND. But VREF is connected to 5V power supply. 

Would you check if the customer's schematic is correct? If ISEN pin is shorted to GND, is VREF pin keeping floating 

or connected to a power supply?

Best Wishes,
Mickey Zhang
Asia Customer Support Center
Texas Instruments

  • 0
    TI__Guru** 114905 points
    Hi Mickey,

    The schematic looks good. VREF should be connected to a supply voltage less than or equal the recommended datasheet maximum.

    Please note the two 0.22uF caps may create overcurrent conditions when the motor is starting. If the current is above the overcurrent limit after the blanking time the device will enter an overcurrent condition.
  • 0 in reply to Rick Duncan
    TI__Genius 12080 points

    Hi Rick,

    Thanks for your reply. If the customer  supplies power to the DRV8870 device first, then IN1=0, IN2=1,

    the motor cannot be started and the motor has a buzz. The output waveform is in the attach.

    If the customer uses  IN1=0, IN2=1 first, then  supplies power to the DRV8870 device, the motor can be strarted well.

    Would you explain this？

  • 0 in reply to Mickey Zhang
    TI__Guru** 114905 points
    Hi Mickey,

    When supplying power to the DRV8870 first, then IN1=0, IN2=1:
    The most likely cause is an overcurrent event. The repeatable 3ms pattern is an indication.
    The inrush required to charge the two 0.22uF load capacitors is probably the reason.

    When setting IN1=0, IN2=1 first, then supplying power to the DRV8870:
    The device begins to operate at ~6.5V. The inrush current into the two capacitors is less and does not activate the overcurrent protection.
  • 0 in reply to Rick Duncan
    TI__Genius 12080 points
    Hi Rick,

    What is the 6.5V voltage that you said?
  • 0 in reply to Mickey Zhang
    TI__Guru** 114905 points
    Hi Mickey,

    The 6.5V is the minimum operating VM voltage. The actual specification is VUVLO, which is 6.5V maximum. So the device can begin operating at less than 6.5V.