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DRV8823: DRV8823 diagnostics

Part Number: DRV8823
Other Parts Discussed in Thread: DRV8412, DRV8844, DRV8802, DRV8806, DRV8873-Q1, DRV8847, DRV8873

Hello,

I'm searching for a chip that can drive at least 2 DC brushed motors at 1,5A peak with SPI control (final solution will have to control 36 motors from 1 MCU).

DRV8823 seems perfect for the job except that, if I understand correctly, it doesn't provide any diagnosis when a protection feature is triggered.
That is a problem because, if the MCU sends a command to drive a motor and it doesn't turn (the MCU gets motor position from an ADC) and no motor current is detected (a series shunt resistor + bidirectional diff amp will sense the current inline with the motor), we have no means to know if either :

  • The motor is not connected
  • One of the DRV8823 protection was triggered and it is waiting for a Vm reset

Am I correct ?

It is desirable to be able to know easily if a motor is badly connected or damaged, and to be able to distinguish this from a H-bridge fault.
Would you have any insight about this ?

Thank you, have a nice day,

Martin

  • Hi Martin,

    Most of our other devices have at least some kind of fault indication on the output. The DRV8823 appears to be one of our earlier devices which does not provide fault indication with the protection features.

    We have many devices that meet your current requirements and have an nFAULT pin: DRV8412, DRV8432, DRV8802, and DRV8844. Would one of these work for you?

    The DRV8847S and the DRV8873-Q1 are two SPI devices with integrated load detection. We're looking at including those features in future H-bridge drivers, so keep checking back for new products. The DRV8806 also has open-load detection, but it is only a low-side driver.
  • Hello James,

    Tank you for your reply.

    Since I need to control 36 motors with only 1 reasonably small MCU (no BGA nor TQFN here), SPI control is almost a need as it lowers the need for external port expanders. It also seems that it is a must to get open load detection (which is really desirable).

    The motors used are 24V, so no DRV8847 unfortunately (but if it was 24V+, it would seem perfect).
    DRV8873 seems nice (although a bit too big as it controls only 1 motor), but when will it be available ?

    If I must switch to non-SPI H bridges, do you know how I could implement open-load detection ?
    I suppose that, if I have a current sense resistor in series with the motor, open load condition can be confirmed if no current is sensed and no fault is sent by the DRV8802 (for example).

  • Martin,

    I believe we are targeting the end of the year to release the DRV8873-Q1.

    I think your suggestion of using a current-sense resistor would work.

    Here are a couple other threads on open load detection that I hope can help:
    e2e.ti.com/.../2393214
    e2e.ti.com/.../454756

    I'll pass your feedback to the system engineers on my team for future product definition.
  • James,

    Thank you for your help.

    The other threads are interesting, I think the open load detection described would work.

    Have a nice day,

    Martin