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DRV8906-Q1: Overcurrent in parallel mode

Part Number: DRV8906-Q1

Hi Team,

My customer had the following question:

If a single output is loaded, the driver switches off in the worst case at 1.3A.


In the worst case, how much current can the driver drive at least before switching off if you now switch four outputs in parallel?

The simplest invoice would be 4 x 1.3A = 5.2A

But now when you assume that the internal FETs have slightly different resistors, the 5.2A are not exactly equalized, but one driver output has a little more and the other driver output has slightly less current. Can it happen that the driver output shuts down with the slightly higher current already if the other driver outputs that have not yet reached 1.3A?
Do we have to assume that no 5.2A can be driven in the parallel connection in the worst case?

Thanks and best regards

David

  • David,

    You are correct that the "current sharing" will not be perfect, so the ideal calculation of 5.2A will not be exact in the real world as one channel may hit OCP before the other.  I would add some tolerance on this to account for Rdson variation.  10% should be more than enough as the FETs are on the same die and channel-to-channel matching is pretty good.

    Regards,

    Ryan