This thread has been locked.
If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.
Hi Alex,
The accuracy is not great at about +/= 25% over temp with about a +50mA dc offset for the 13-15 bit settings. The 12-bit setting will always read low and is not recommended.
Regards,
Jeff
Hi Jeff,
Thanks for the tip.
And what is the ADC accuracy for the voltage rails: VBUS, VBAT, etc?
Alex,
The voltage rail accuracy is slightly better but has a similar +50mV offset.
Regards,
Jeff
Hi Jeff,
I was under impression that the low accuracy of the current sampling is due to inaccurate I->V conversion, which should not be an issue with direct voltage sampling.
I expected the voltage sampling accuracy to be mostly a combination of bandgap accuracy (which seems to be 0.5% based on the voltage regulation tolerance figures) and the matching accuracy of the internal sampling capacitors (probably few %).
The 50mV offset is not a problem for me, but if you're saying the overall accuracy is slightly better than +/-25% then I'm a bit concerned. It means that when sampling a 2S battery voltage of 7V the reading might say anything between 5.25V and 8.75V, which is a pretty wide range when it comes to battery voltage.
A gain error of 1% or 2% would seem like a more reasonable accuracy figure. The sample that I'm testing seems to be pretty accurate when it comes to voltage sampling, but I did not test it at different temperatures.
Can you please double-check? It's very important for my design.
Hi Alex,
The charger doesn't use the ADC for regulation. The ADC is only for a reasonableness check. Unfortunately, I don't have accuracy data that I can warranty. The above numbers were derived from measurement taken on a few units over temp but not a true statistical sample.
Regards,
Jeff