DRV8872: Fault signal triggering

Ibram Sahibu

Part Number: DRV8872
Other Parts Discussed in Thread: DRV8816

Hi Guys,

We are using DRV8872 in our design. We selected this part because of the fault signal feature but it is not working as we thought.

I have to set the current limit of ~1.2A using ISEN pin and I am expecting a fault signal whenever the current hits this limit. But there is no change in fault signal state when it reaches the current limit.

But I was able to see Fault signal on when I remove the current limiting and let it run with the max current of 3.6A since min Iocp is set to 3.7A.

I would expect the Iocp to match current limiting values so that we can make use of fault feature completely. Else whenever there is a some current limiting less than 3.6A then there is no way we could enter OCP condition.

Could you guys clarify this for me ASAP?

Regards,

Ibram

over 7 years ago

0 Rick Duncan over 7 years ago

TI__Guru** 114905 points

Hi Ibram,

The fault signal is not asserted when the device is regulating current using the ISEN pin. This is not an overcurrent condition, and is considered normal operation for the device.

If you want a device to assert a fault when a user defined current level is reached, please look at the DRV8816.

0 Ibram Sahibu over 7 years ago in reply to Rick Duncan

Prodigy 150 points

Hi Rick,

Thanks for your response and suggestion.

It seems like DRV8816 is providing what I was expecting in DRV8872. Is there any way you can bring that feature in DRV8872? Else, please suggest me the part with same footprint as DRV8872. I am also ok with 1 half bridge.

Regards,
Ibram

0 Rick Duncan over 7 years ago in reply to Ibram Sahibu

TI__Guru** 114905 points

Hi Ibram,

That feature is not available in the DRV8872. You can create a circuit to monitor when the device is chopping and perform an action using a mcu.

An example of the chopping monitor circuit can be seen here: www.ti.com/.../slva858.pdf

There is no device with the same footprint and ability to disable the output when a current level is reached.

0 Ibram Sahibu over 7 years ago in reply to Rick Duncan

Prodigy 150 points

Hi Rick,

It seems that the example described (Figure.4) in www.ti.com/.../slva858.pdf is applicable only when PWM of motor driver input set to 100%. Please confirm that.

In our application PWM will be set between 50% to 100%.

Regards,

Ibram

0 Rick Duncan over 7 years ago in reply to Ibram Sahibu

TI__Guru** 114905 points

Hi Ibram,

That is correct. This works when running at 100%.

In many applications, current regulation can be used to limit the startup current and stall current. Once the motor is running the current is much less.

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DRV8872: Fault signal triggering