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
]]>
0 Comments