DRV8833: precise function of the nFAULT pin

Simeon

Part Number: DRV8833
Other Parts Discussed in Thread: DRV8881

Hi everybody,

In a previous question i asked some questions about the possible values for Rsense on this IC.

I assumed that once the current through the motor exceeded the set limit (Ichop), the nFAULT would be pulled low.
However in practice this did not seem to happen.

Is it true that Rsense is used to set the current control circuit which fuctions as a torque limit circuit.
And, that nFAULT only is pulled low whenever the Iocp (2 - 3.3A) is reached?

This would mean nFAULT cannot be used as a stall detection signal.

Thanks in advance for clarifying.

Simeon.

over 1 year ago

0 Jacob Thompson over 1 year ago

TI__Mastermind 23261 points

Hey Simeon,

Are you driving a stepper motor or 1x or 2x Brushed DC motors?

Check out 7.3.3 Current Control in the datasheet. ICHOP is for current regulation - it will try to keep the current at or below the chopping current set. Overcurrent protection is what would trip nFAULT and disable the outputs.

Also see this diagram about how current regulation works from DRV8881. It isn't exactly the same since it calls the term "ITRIP" instead of ICHOP, but the concept is the same:

Is this a new design? I recommend using a newer device with a IPROPI output (look for Integrated Current Sense as a feature here - https://www.ti.com/motor-drivers/brushed-dc-bdc-drivers/products.html#248=2%3B6&2192=Integrated%20Current%20Sensing%3BCurrent%20sense%20output%3BIntegrated%20current%20sense&2716max=12%3B115&)

I think that DRV8424E will fit you much better.

Best,

Jacob

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DRV8833: precise function of the nFAULT pin