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DRV8873: OverCurrent Protection

Part Number: DRV8873

Although OCP is programmed at 4A, no limitation occurs with 5.7A load.

I use the SPI version, program the lowest current limit, but at 13.5V through 2Ohm power resistor I get 5.7A and no OCP, what am I missing ?

Below are the values read from the registers (comments added to my program output) while starting and turning the power on for 4s (poll each 200ms):

— Registers after initialization

FAULT 00

DIAG  00

IC1   FD

IC2   0C

IC3   40

IC4   00

— Registers 0 and 1 polling each 200ms

FAULT 00

DIAG  00

FAULT 00

DIAG  00

... 16 more times the same FAULT/DIAG

FAULT 00

DIAG  00

FAULT 00

DIAG  00

— Registers after 4s powering

FAULT 00

DIAG  00

IC1   FD

IC2   0C

IC3   40

IC4   00

  • Hi,

    The IOCP limit for the DRV8873 is 10A. It is a fixed value. 

    The DRV8873S has on-chip current regulation. The current is regulated at the Itrip level set by ITRIP_LVL bits in the IC4 control register. In your settings IC4 = 0x00. I trip level is 4A. If you look at the current waveform it should be similar to described in the datasheet with inductive loads such as BDC motor. 

    However, with resistive load as in a power resistor used by you, due of lack of inductance the rise and fall times don't work as described and you'll have to provide a series inductor for current regulation to work. Alternatively you can disable the current regulation and reduce the power supply voltage to achieve the desired current.

    The Itrip setting is not related to OCP. 

    Regards, Murugavel

  • Hi,  sorry for my late answer, I watched a cold in the meantime.

    Firs of all sorry for the bad terminology, I was indeed referring to current regulation.

    And you are right, the current regulation kicks in with an inductive load, seems this would deserve a note in the Data Sheet...