DRV8332: Current Sense questions regarding example schematic on page 26 in DRV8332 datasheet.

Greg Basile57785

Part Number: DRV8332

I have 2 Questions regarding the example schematic found on page 26 in the DRV8332 datasheet. For reference here is a snippet of the current sense circuit:

For differential operation should R28 = R32. If the difference is correct, please explain the reason for it.
What is the purpose of adding C19 and C25?

Thanks,

Greg

over 5 years ago

0 Adam Sidelsky over 5 years ago

TI__Guru 61310 points

Greg,

As the original designer is no longer in the group, I'm not certain why these two values don't match but their value is probably not super critical.

For C19 and C25, these are for forming an RC filter at the op-amp input.

Regards,

-Adam

0 Adam Sidelsky over 5 years ago in reply to Adam Sidelsky

TI__Guru 61310 points

Greg,

I will close this thread due to inactivity, please post again if you have further questions.

Regards,

-Adam

0 Greg Basile57785 over 5 years ago in reply to Adam Sidelsky

Intellectual 430 points

Using voltage superposition, set the reference voltage (2.5V) to 0V. R48 (15.4K) and R40 (30.1K) are now in parallel and have a value of 10.18 which is basically equivalent to the feedback resistor R24 (10.2K). This is what one would expect for a differential amplifier circuit. I believe the correct value for R28 should be 931.

Changing R28 from 631 to 931 changes the offset voltage of the output from ~1V to ~1.5V. This change increases the current measurement range.

The RC configuration is a high pass filter with a pole at 770 KHz. I do not know why this would be desired.

0 Adam Sidelsky over 5 years ago in reply to Greg Basile57785

TI__Guru 61310 points

Unfortunately I cannot comment on why the original designer picked these values. Please post again if you have further questions.

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DRV8332: Current Sense questions regarding example schematic on page 26 in DRV8332 datasheet.