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DRV8833: Current Limiting & Fault Functionality

Hayden_Hast
Intellectual 1515 points
Part Number: DRV8833

Hello,


I am doing testing with the DRV8833 and the current limiting function on a project.

 

I have the ISEN set and I can see that when this node voltage rises, the DRV8833 does begin its cycle-by-cycle limiting and disconnecting/reconnecting the output around the ~50kHz internal frequency. However, I have (almost) never seen the FAULT pin trigger during this limiting. Is this expected behavior of the part? We were hoping to use the FAULT pin as a feedback to help the system know when overcurrent or current limiting events have triggered.

 

I am measuring that during the cycle-by-cycle limiting, the overcurrent only lasts for ~3us before the output shuts off. But the OCP Deglitch Time in the datasheet is 4us min, meaning that if the cycle-by-cycle limiting is operating, we would never observe a FAULT. Is this normal behavior? Is there any way to get Fault feedback in this mode?

 

Thanks,

Hayden

  • 0
    TI__Guru** 114905 points
    Hi Hayden,

    Yes, this is normal behavior.

    There is a difference between current regulation and overcurrent. Current regulation occurs during normal operation and does not assert the nFAULT pin. Overcurrent is abnormal operation and asserts the nFAULT pin.

    If you want to determine when current limiting is occurring, there is a reference design that may help. The link is www.ti.com/.../tidu302a.pdf

    The concept could apply to the DRV8833 assuming slow decay is used when regulating.