INA290: Incresing Voltage Offset on Current Sense

Steven Richardson

Part Number: INA290

Hi, I am using a INA290A3 to measure a 12V load using a 6mR shunt resistor.

I have an issue whereby the output read at the current net below has a positive offset that appears to increase with current.

It is out of spec for resistor tolerance and also input offset voltage giving an offset of up to 266mA at 5.5A.

The circuit is below and I have tried removing the input filter (R15, R19 and C6) and also disconnecting R16. I've even used a resistive load as well as a DC programmable load.

Is there someway I can improve on this as the is a lot less accurate that I would expect from this chip.

Thanks

Steven

over 1 year ago

0 Javier Contreras4 over 1 year ago

TI__Mastermind 33170 points

Hello Steven,

You may want to remove R15 and R19 and place 0Ω resistors in there place. The IB on the INA290 is in the 20µA but this still does not explain the rest of the error. There will be a difference between the inputs due to IB but I do not expect that much.

Have you measured across the Rshunt and at the inputs to see if there is a difference? How are you layout with the senor. If seems like a gain error and not an offset which could be caused by an unexpected Rshunt value which could be due to layout.

Regards,

Javier

0 Steven Richardson over 1 year ago in reply to Javier Contreras4

Prodigy 30 points

Hi, I've tried with R15 and R19 as 0R but that didn't help. The layout is as below. Input 12V bottom right via a plane and exit top right via plane.

0 Javier Contreras4 over 1 year ago in reply to Steven Richardson

TI__Mastermind 33170 points

Hello Steven,

I think it is the layout. To prove this measure across your shunt right on top of the resistor and measure at the inputs of the INA290 with something that can distinguish the 480µV error. I think you will see a difference. I have pasted the layout recommendation.

0 Steven Richardson over 1 year ago in reply to Javier Contreras4

Prodigy 30 points

Hi, I have updated the design to use a Littel Fuse L4CA0612LR006FNR 4 terminal sense resistor in the hope to improve accuracy.

I have also removed the input filter as I assume even zero ohm resistors would not be matched and could cause issue.

Hope this will help

0 Javier Contreras4 over 1 year ago in reply to Steven Richardson

TI__Mastermind 33170 points

Hello Steven,

I think this will help as this is better than my recommendation. I hope you were able to verify the issue with the measurements I suggested. Normally when it is a layout issue like this the gain is larger than expected as

Regards,

Javier

Amplifiers

Amplifiers forum

INA290: Incresing Voltage Offset on Current Sense