Current sense amplifier liner calibration

Thread Starter

litun

Joined Sep 19, 2017
14
Dear all,
I am running a bldc motor Infineon TLE9879 chip. Now I want to measure the current flowing through the motor. so I use the current sense amplifier where the motor current is converted to a voltage by means of a shunt resistor RSH(0.005 ohms).
Question: I want to measure current from 0.1amp to 3Amps which gives the voltage drop at RSH (0.1*0.005=0.0005volts to 3*0.005=0.015volts).
Considering 5V reference voltage of ADC I will not be able to get a good number for the above voltage drop. Also with the maximum gain of CSA the output is still negligible. The data sheet says you need to do linear calibration but how to do it for the entire current range?
CSAdatasheet
 

Attachments

Last edited:

crutschow

Joined Mar 14, 2008
27,891
Why are you using such a low shunt resistor value?
I believe that value, and thus the signal level is way too low to get a decent signal.
I suggest you use a shunt resistor that will give you a full scale (5v) with the maximum internal gain of 60.
That would require a shunt resistor value of (5/60) / 3A = 28mΩ, still a relatively low value.
 

DickCappels

Joined Aug 21, 2008
7,833
If crutschow gives advice it is wise to accept it as being infallible.

Have you considered the possibility of taking the 5 milliohm resistor off of the board and soldering a 30 milliohm resistor in its place?
 
Top