Other Parts Discussed in Thread: LM5066I
Hello. I am seeing a large offset voltage on the Shunt Voltage measurement register at no load. With a 1.5m ohm sense resistor, Vin of 24V, and IC output disabled the shunt voltage is measured at 275uV. This corresponds to a 182mA offset current.
I have three ICs on my board and they all show similar offsets. Changing the sample time and averaging does not improve the offset. However, the offset does appear to be dependent on the input voltage level.
Decoupling the input voltage and the logic rail (3.3V) going to Vs allowed me to ramp the input voltage at no load and observe the offset. Below are some sample values:
Vin: 28.454V
ADC Measurement: 0.220A
Vin: 24.006V
ADC Measurement: 0.185A
Vin: 12.395V
ADC Measurement: 0.095A
Vin: 05.596V
ADC Measurement: 0.043A
Vin: 03.309V
ADC Measurement: 0.023A
Is this behavior expected for the device? The amount of error I'm seeing does not match the stated worse-case CMRR in the datasheet but it's possible I'm missing another error source.