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DRV8832: Peak motor drive output current

user5163865
Genius 3980 points
Part Number: DRV8832

Hi,

Our customer are evaluating the DRV8832.
Please let me know if there are any problems with the circuit design.

Motor start-up current: 457mA typ
Over load (Lock) current: 1.3A
Rshunt: 0.15 Ω (200mV/0.15 = 1.33A)
VDD: 4.3 V
VSET: 3.12V

According to D/S, "Continuous motor drive output current" is 1A.
Should the current limit be lowered?

On the other hands,I understand that "Peak motor drive output current" is a specification of instantaneous current.
I think this design is not a problem if this specification is considered.

Please give me advice as one of the 20 prototype circuits may have destroyed the IC by EOS.
The cause is unknown.
After power-up, as soon as IN1 or IN2 is set to Hi, Fault is asserted.
The other 19 work fine.

Best regards,
Hiroshi

  • 0
    TI__Guru** 114905 points
    Hi Horishi-san,

    "After power-up, as soon as IN1 or IN2 is set to Hi, Fault is asserted."

    What is the time between IN1 or IN2 set to Hi and FAULTn assertion?
    Does FAULTn de-assert after some time? If yes, how long between assertion and de-assertion?


    There are a few items to consider to protect the motor from excessive currents when stalled:

    1) If the startup current is 457mA and the lock current is 1.3A, please consider changing the Rshunt to ~220 (current limit of .72A to 1.1A).
    This will control the motor during startup and stall conditions. It will also cause the FAULTn to assert indicating a stall condition after ~275ms.
    Please note some motors may not indicate a stall. The stall is indicated if ~12300 consecutive PWM cycles reach the current limit. If any one PWM cycle does not reach the current limit, the timer is reset and the count begins again.

    2) VSET was designed to be connected to VREF or a resistor divider based on VREF.
    It is recommended to change the connection. This should not cause a problem, but should be corrected.
  • 0 in reply to Rick Duncan
    Genius 3980 points

    Hi Rick-san

    Thank you for the advice.
    Since I only have waveforms in the 500ms range, the exact value is unknown but is asserted with a 10~30 us. Also, it is not asserted.

    I will explain to them about Vset and Rshunt.
    Thank you again.
    Best regards,
    Hiroshi