INA195: INA195 no load output offset voltage

Evan Hall

Part Number: INA195
Other Parts Discussed in Thread: INA194, INA193

I am using the INA195 to sense current through an inductive load on the low-side of the load. I have implemented a high-side and low-side switching scheme (essentially an H-bridge) to enable the load. When both the high-side and low-side MOSFETs are not conducting I am seeing variation in the output voltage anywhere from a few millivolts to over a hundred millivolts. Is this type of behavior expected? We are sensing the load over a 0.1ohm resistor.

over 5 years ago

0 kai klaas69 over 5 years ago

Guru 140200 points

Hi Evan

I guess in this moment there's no longer a path for the input bias current of INA195 to signal ground?

Kai

0 Evan Hall over 5 years ago in reply to kai klaas69

Prodigy 20 points

There is ~ 135kOhm to the 5V return that is powering the device on both the (+) and (-) inputs.

0 Peter Iliya over 5 years ago in reply to Evan Hall

TI__Mastermind 26710 points

Hello Evan,

Thanks for posting to the forum. The short answer is yes this behaviour is expected. The zero-current output voltage (VOUT) for INA195 can be quite high, espcially when Vsense≤20mV and 0V≤VCM≤VS. For this scenario we spec the VOUT for INA195 at 2V maximum and this is in datasheet (see below).

In your case, you have INA195 devices either with input pins grounded (VCM=0V) or tied to 5V rail (VCM=5V). I am not sure what your VS voltage is, but I assume it is close to 5V. You can make the maximum VOUT lower by using a lower gain device (INA194 or INA193) or ensuring VCM > VS.

Hope this helps. Please post back if you need more design information.

Sincerely,

Peter Iliya

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INA195: INA195 no load output offset voltage