INA280-Q1: INA280 CURRENT WRONG

Hi Mustafa,

Mustafa Torbali said:

But Current is wrong.  There is a logarithmic increase.

We can help you but we need way more details. So please post a schematic and specify the error.

I have some ideas about potential causes but I don't want to speculate and to guess.

Kai 

Thank you.

There is my schmatic.

I measure VIN total current with ampermetre. This is different INA280 with my ampermetre. 

It measures current when there is no voltage at the input and ~25mA is measured by the INA280.

Hi Mustafa,

you mean, there's nothing connected to the inputs of INA280? The INA280 cannot work with fully floating inputs.

What shunt do you use? Please add the input circuitry to your schematic and post a complete schematic.

Kai

Sorry about that

.

Shunt Resistor is 0.002 Ohm.

Hello Mustafa,

When you are looking at the low end of a unidirectional current sense amplifier you need to look at a couple of specifications to see the lowest value you can measure.

The first is swing low.  Max is 25mV and typical is 5mV from GND.  This limits how low you can measure.

Vout = 25mV translates to 250mA.  25mV/50(V/V)/0.002Ω 

Vout = 5mV translates to  50mA.  5mV/50(V/V)/0.002Ω 

The other concern is the Vos of the device.  Vos max is 150µV.  

Vos error 150µV translates to 75mA.  150µV/0.002Ω.

Regards,

Javier

Mustafa,

Please let me know how else I can help.  If you need an alternative I would need some more inputs.  You could use a bi-directional device but then you would need to place a reference voltage.  If you are willing to use a bidirectional device there are some options.