SM72295: SM72295 resolution issue

Hi Hsu,

thanks for reaching out about this. from the looks of your excel data the current sense amp IIN output is measuring anything below 0.5A as 0A?

with such low current voltage reading the accuracy might be drowned out by noise. Can you share the schematic including the sm72295 and fets?

can you confirm the IIN node has a clean voltage?

Thanks,

The circuit  is for your reference,thanks.

Solar board.pdf

Thanks Hsu,
can you confirm that SOA is connected to R197?
can you confirm the dynamic range is 0 to 5A?
does the issue remain with when using higher gain?
Thanks,

The measurement results(IIN Volt) are as follows(GAIN SET: 100Kohm/402 ohm)

0.3A~0.8A measurement data looks linear,0.9A~5A measurement data looks Nonlinear, Why?

Please help us with suggestions.

Hi Hsu,

thanks for your update,
Since RL is 10k the gain is only about 20. Increasing the gain might help the accuracy in a noisy environment.
in the sch SOA is floating - can you confirm that SOA is connected to R197?

the smaller the shunt the smaller the current that can be sensed however the larger the error
for a same sized shunt a larger current will produce a smaller error which is not representative of the data
the expected uncalibrated error is less than 5% however your data shows a 25% error
I noticed that the current sense output only goes to 3.1V for max load. If using VDD as 3.3V then the voltage at IIN at max load should be 3.3V in order to provide enough signal to noise ratio for such a small 2mohm shunt.

Thanks,

The SOA is connected to R197, Can I improve this problem if I change IIN to use BIN?

Hi Hsu,

Can you confirm voltage on BIN pin is more linear or less similar to the uC output?

Can we scope IIN during 5A load to determine is noise is affecting the signal?

Is the performance of IOUT ok?

Thanks,