DRV110: Protection of SENSE Pin

Patrick Ruf

Part Number: DRV110

Hi,

We use the DRV110APWR to switch a valve. So far the device works as it should. The schematic is as follows:

Now we have the problem that users can connect a 24VDC supply to the valve connector J18. So that pin 1 of J18 ist +24VDC and pin 2 of J18 is GND.
And, unfortunately, if they can connect a 24VDC supply, they will do so.
The problem is that in such a case the voltage at pin 9 (SENSE) of the DRV110 will see a negative voltage relativ to its GND that is dependent of the supply current flowing through R1015.
This voltage is specified as -0.3V absolut max. in the datasheet.

Question:
Is it possible to protect pin 9 (SENSE) of DRV110 with a resistor to limit the current into pin 9? Any drawback for the normal operation? I would see a resistor in the range of 470 Ohm.

Thanks and best regards,
Patrick

over 1 year ago

0 Pablo Armet over 1 year ago

TI__Mastermind 37683 points

Hi Patrick,

Thank you for posting to the E2E forum. I will be supporting you with your questions.

In order for me to better understand the problem you are observing, can you provide waveforms of the sense voltage and any other signals of interest?

Regards,

Pablo Armet

0 Patrick Ruf over 1 year ago in reply to Pablo Armet

Genius 4880 points

Hi Pablo,

Unfortunately I have no waveform yet. But you can see it as a static situation that looks as follows:

If the supply current from the external supply that was (by mistake) connected to J18 rises over 0.638A the voltage at U4 pin 9 (SENSE) will be higher than the specified maximum voltage of -0.3V (probably the voltage limit for the ESD protection diodes inside the DRV110). The resistor (Protection resistor) will then limit the current into pin 9.

Actually my question is (probably) already answered as I have seen in the datasheet that one can add a RC filter to pin 9. And example schematics I have seen have a 1k resistor in the sense path with a 100pF filter capacitor.

Regards,
Patrick

0 Pablo Armet over 1 year ago in reply to Patrick Ruf

TI__Mastermind 37683 points

Hi Patrick,

Apologies for late reply. I was out of office yesterday.

Yes, you can add a resistor to limit the current going into the SENSE pin. Although I'm not sure if this will help with the negative voltage but it is worth a try. It seems to me that the voltage is due to the voltage drop across the sense resistor when current direction is reversed. My suggestion is to choose a lower SENSE resistor and recalculate the PEAK and HOLD resistors as needed.

Regards,

Pablo Armet

0 Patrick Ruf over 1 year ago in reply to Pablo Armet

Genius 4880 points

Hi Pablo,

I will try it with a 1k Resistor in the SENSE path.

Regards,
Patrick

0 Pablo Armet over 1 year ago in reply to Patrick Ruf

TI__Mastermind 37683 points

Patrick,

Sounds good. Let me know if that resolves the problem.

BR,

Pablo

0 Pablo Armet over 1 year ago in reply to Pablo Armet

TI__Mastermind 37683 points

Hi Patrick,

Any updates?

Reards,

Pablo Armet

0 Patrick Ruf over 1 year ago in reply to Pablo Armet

Genius 4880 points

Hi Pablo,

Not yet. I expect first results next week.

Regards,
Patrick

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DRV110: Protection of SENSE Pin