MM912J637 - using VOC and VSGC to help compensate external circuit

[ianwilson]

Hello all,

We have a small resistance (a fuse) in the lead feeding VSENSE and also powering the circuitry.  Current consumption changes therefore have a small effect on the measured voltage.  We have a state where a reasonably well known increased load on our circuit is switched in.  So we know when there is an extra current draw through the fuse.

We can work out suitable offset (and maybe gain) corrections (in the order of 5mV or less).

It seems to me we can tweak the VOC offset compensation register to also include our external circuit offset as well as the device offset. But only if there is sufficient range in the 637's compensation registers.

This will depend on the range of offsets we expect to see from the device itself.  From the datasheet the 637's compensation range is ~ +/- 9 mV with resolution of about 0.07 mV.  However, we don't know range is normally used by the devices. I.e. what is the production spread.

Is there any information on the spread of offset and gain compensations across production?

Many thanks,

Ian Wilson

[TomasVaverka · Accepted solution]

Hi Ian,

I see no problem of using the VOC offset compensation register to compensate some additional +/- 5mV.

The ~+/-9mV given in the datasheet refers to the SD input voltage of 0…1V. The VSENSE has a divider 28:1.

Regards,

Tomas

PS: If my answer helps to solve your question, please mark it as "Correct". Thank you.