Designing a current sensor with INA180

Designing a current sensor with INA180

 

Calculating the sense resistor value:

Load Current = 1A
Gain = 50
Maximum input at the INA180 terminals for 3.3V maximum supply voltage = 3.3/50 = 66mV
For Maximum load current of 1A, the maximum value of resistor is 66m/1A = 66mohm

This meant any resistance beyond 66mohm shall have a saturated output Op-Amp and we cannot calculate the full-scale current

Power requirement for the sense resistor = 1A*1A*66mohm = 66mW

Calculating the minimum value of voltage that can be measured:

The voltage offset of the INA180 for +V rail of 12V is 0.5mV. Considering this scneario, a 10mA current can be comfortably measured by the operational amplififer without any issues

10mA*66mohm = 0.66mV which is more than the offset voltage

As the Common mode voltage on +V gets reduced, much lower currents can be measured.

Filter design:

RC filter is used to filter out the out of band noise. Filter is used at the output of the Current Sense Amplifier. 
A cut off frequency of 16KHz is considered for the filter. Further, the cut off can be changed by modifying either the R1 or C1 value.

Cutoff frequency can be calculated using 1/2*Pi*R1*C1

Post a Comment

0 Comments