INA181: Output does not match ADC reading

Kenneth Kong

Part Number: INA181

Hello!

I am using INA181A1 (Gain = 20) in my design and its output is directly connected to an ADC input of my microcontroller (STM32G070CBT6).

All it does is to help me monitor the current consumed on my 3.3V rail on my board.

The configuration is as follows:

The issue I am seeing is that the voltmeter measures 34mV at the output of this amplifier but my ADC reading (12-bit and Vref = 3.3V) is showing a different value (it calculates to 100mV by using formula...

What could have possibly gone wrong here?

I am quite new to this type of integration and apologize if this question already exists on this form but would still appreciate any feedback here!

Thank you!

Regards,

Ken

over 6 years ago

0 Peter Iliya over 6 years ago

TI__Mastermind 32395 points

Hello Kenneth,

Thank you for posting to the forum.

I am bit confused as to what your measurements/calculations are.

What is the Vref = 3.3V referring to? Is this the internal reference voltage of ADC? If so, this should probably be connected to INA181 REF pin.

Is your 34mV measurement taken from OUT to REF or OUT to GND? It seems REF is tied to GND. If this is the case, then 34mV output measurement may be too low of a measurement for the ADC?

Or is the 34mV the shunt voltage?

In order to help you best, please detail values of the current (ILOAD), VOUT, ADC readings.

Also, please consider viewing our training videos to better understand these devices.

https://training.ti.com/ti-precision-labs-current-sense-amplifiers-gain-error?context=1139747-1139745-1138708-1139852-1140045

Sincerely,

Peter

Amplifiers

Amplifiers forum

INA181: Output does not match ADC reading