If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

# INA282-Q1: INA282-Q1:

Part Number: INA282-Q1

Hello,

We are using external ADC (ADS1118IDGSR) . for current sensing by IC INA282-Q1. We have connected shunt resister of value 0.0001ohm(connected 0.0003ohm in parallel manner) at high side of battery. we have configured device INA282-Q1 in following manner.

so we are following below mentioned steps to get physical value of current from raw value.

A programmable gain amplifier (PGA) is implemented before the ADS1118 core. The full-scale range is configured by three bits (PGA[2:0]) in the Config Register and can be set to ±6.144 V, ±4.096 V, ±2.048 V,±1.024 V, ±0.512 V, ±0.256 V.

LSB = FSR / 2^16 (Datasheet)

FSR= ±4.096 V we are using

LSB=125microV

INA282Q1

INA 282 Q1 purpose here -

• Its providing the gain of 50
• Its using the zero drift.

The O/P pin of this IC is having the minimum voltage range as (GND-0.3)V

The VREF1 and VREF2 that we are using is 2.5V.

Calculation-

we are getting raw count as- 20071

The EADC OP voltage will be- LSB*20071

LSB=125microV

So EADC Output V= 125micro*20071=2.508875 V

Since, we were adding the offset of 2.5V so the voltage will be 2.508875-2.5=0.008875V

This was given a gain of 50, so the V will be=0.00875/50=0.000175V

The resistor used is 0.0001ohm

So current will be 0.000175/0.0001=1.75A

For this calculation we are not getting expected current value. so kindly let us know, if we are missing something?

Regards;

Utsav Shah

• Hi Utsav,

There could be a number of things that cause the measurement discrepancy.

I would look into the 2.5V reference voltage. Have you measured it with the same ADC to account for error?

Also the input offset of the device is ±70uV, which is comparable to the ~175uV input. It is possible that the percentage error is too big at low level input voltage. You may want to increase the load current, therefore the input voltage, to reduce the impact of Vos. The correlation should improve.

Regards, Guang