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DRV8848 - OCP function

Other Parts Discussed in Thread: DRV8848

Hi all

Would you mind if we ask DRV8848?

The datasheet shows about OCP function as following;

<OCP function>
An analog current limit circuit on each FET limits the current through the FET by limiting the gate drive.
If this analog current limit persists for longer than the OCP deglitch time tOCP,
all FETs in the H-bridge are disabled and the nFAULT pin is driven low. The device remains disabled until the retry time t RETRY occurs.
The OCP is independent for each H-bridge.
Overcurrent conditions are detected independently on both high-side and low-side devices;
that is, a short to ground, supply, or across the motor winding all result in an OCP event.
Note that OCP does not use the current sense circuitry used for PWM current control, so OCP functions even without presence of the xISEN resistors.

<Question1>
About the word "OCP deglitch time tOCP",  if it is the deglitch time, is it tDEG?
Or, with including the deglitch time tDEG, does it show tOCP(Overcurrent protection period)?

<Question2>
We can't find what tRETRY indicates on the datasheet.
So, what is tRETRY? Is it possible to set the number of tRETRY?

We need your help.

Kind regards,

Hirotaka Matsumoto

  • Hi Hirotaka,

    Please refer to the following answers.

    Q1: Yes. It is the tdeg (2.8us).

    Q2: tRETRY is actually tOCP(1.6ms)

    So if the shortage condition is presented all the time, the output will be ON for 2.8us and OFF for 1.6ms and cycling. This produces a very small duty regulation which only have about tens of mA level outputs. When anytime the OCP event removed, the outputs back to normal loading level.

    Best regards,

  • Hi,
    We are using DRV8848 in our project.
    We want to know about current sensing resitors used in each bridge.
    As per formula Ifs=Vvref/(6.6XR isense).
    So for R i Sense can we use comman resistor to bothe sense pin to limit the current as per mentioned by the formula.
  • Hi Sagar,

    If you are using parallel mode, you can use a common (one current sense) resistor. If you are using standard non-parallel mode, two current sense resistors are needed.