INA211: Voltage devider on input

Philipp Winter

Part Number: INA211

Hello together,

I want to reduce the output voltage of the INA211, but it is not possible to change the shunt resistor. We are driving the INA211 with an input filter like on chapter 7.4.1 in the datasheet. The idea is to add a resistor parallel to the input pins of the INA211, this reduces the input voltage like a voltage divider. A graphic is in the attachement. We tested it and it works very well. Do you have any experience with that? Does it disturb something?

Best regards

Philipp

over 3 years ago

0 kai klaas69 over 3 years ago

Guru 140200 points

Hi Philipp,

yes, you can do this. But I would recommend to reduce the resistors by a factor of two to make R409 and R410 fall below 10R, as recommended in section 7.4.1 of datasheet.

Kai

0 Guang Zhou over 3 years ago in reply to kai klaas69

TI__Mastermind 27390 points

Hi Philipp,

Let’s assume the differential voltage across R406 is Vshunt which is to be amplified by INA211 without the 150R.

If you accurately measure Vshunt, you’ll probably find out that the gain is modified not by the divider ratio of 0.79. Rather it is by something quite different.

However, since the schematic shows the shunt is made of PCB track which has large tolerance, what you’ve observed are likely the result of two inaccuracies cancelling each other.

It is OK to use this configuration. You’ll likely see some fairly large gain variation, but it is not related to the gain divider circuit itself, rather it is related to the PCB track.

Regards, Guang

0 Philipp Winter over 3 years ago in reply to Guang Zhou

Prodigy 20 points

Hello Kai and Guang,

thank you for the feedback.

Best regards

Philipp

0 kai klaas69 over 3 years ago in reply to Philipp Winter

Guru 140200 points

You are welcome, Philipp :-)

Kai

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INA211: Voltage devider on input