INA290: INA290A2

Zsolt Danyi

Part Number: INA290

Dear Support,

I have a question regarding the INA290A2 chip. I use this chip to measure maximum 3A. My problem is I get a fairly big difference between my multimeter current measurememt and my INA current measurement.To my 39 Ohm load I give 20V, with a multimeter I get 0,51A, on my INA output I get 0,859V which corresponds to my knowledge 0,572A. Could you please give me a hand what can cause this difference between the 2 measurement?
To summarize

Rload=39Ohm; U=20V -> multimeter in series 0,51A. Same measurement on the INA with 30 mOhm shunt resistor gives 0,589V on the INA output and I am using A2 50V/V gain, gives me the factor of 1,5 to divide my INA output to get the current.

Am I right?

Thank you

Zsolt

over 1 year ago

0 kai klaas69 over 1 year ago

Guru 140200 points

Hi Zsolt,

this can have to do with the connection of shunt. If connected improperly to the INA290, you additionally measure the voltage drop across the solder joints which can increase the reading of INA290. Have you connected the shunt as shown in figure 10-1 of datasheet?

A four terminal shunt can also be helpful, especially if you plan to use a lower resistance shunt:

To exclude other error sources, can you show a schematic of your circuit?

Kai

0 Cierra Cowley over 1 year ago

TI__Intellectual 1235 points

Hi Zsolt,

Can you provide the schematic and layout as Kai suggested?

Thanks!

Cierra

0 Zsolt Danyi over 1 year ago in reply to Cierra Cowley

Prodigy 150 points

Hi, thank you, sure.

0 kai klaas69 over 1 year ago in reply to Zsolt Danyi

Guru 140200 points

Hi Zsolt,

as already assumed, the layout arround the shunt is non-ideal. I would recommend the following modifications (compare with figure 10-1 of datasheet):

Or use a 4-terminal shunt.

Another issue is the width of copper tracks running to and from the shunt. To minimize any additional voltage drop across the copper tracks at 3A, I would make the copper tracks a bit wider. The copper track should be at least 1mm wide, better 1.5mm or even more.

Kai

0 Cierra Cowley over 1 year ago in reply to Zsolt Danyi

TI__Intellectual 1235 points

Hi Zsolt,

Kai is correct, the layout here is not ideal.

Please see our current sensing training videos: 1) Current sense amplifier applications > Shunt resistor layout, and 2) Debugging > Debug a current shunt monitor circuit: Layout, for ideal layout practices.

Cierra

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INA290: INA290A2