Excessively high output error (4%) with NPM1100

RE: Excessively high output error (4%) with NPM1100

Sigurd Hellesvik — Mon, 10 Jan 2022 15:21:03 GMT

Another note on the output error.
It is normal for PMICs to have +4% typically in no load condition. The nPM1100 specified -2/+8% and because of that we trim value a bit high with no load condition to cover all cases.

Regards,
Sigurd Hellesvik

RE: Excessively high output error (4%) with NPM1100

peterqu94305 — Mon, 13 Dec 2021 23:58:47 GMT

Hello Sigurd,

Thank you for the reply. For our use case, -2 to +8% error is acceptable. So I think this issue can be closed since the NPM1100 is operate within the specification.

That being said, most of the competing buck regulators or PMIC have error of +/- 2%. We are just surprised (unpleasantly) that the Nordic PMIC has such as a large output error when it is priced at same level as the TI PMIC and a significantly premium compared to PMIC from Asia. Its not a good feeling to pay for a premium price and got a mediocre product.

Thank you,
Peter

RE: Excessively high output error (4%) with NPM1100

Dom O — Thu, 25 Nov 2021 16:39:20 GMT

Hi Peter - I'm getting the same result. 3.113V to 3.114V output, across GND and VOUTB, on my nPM1100-EK, with or without a 20mA load, with or without USB charging connected.

Checked with 2 different voltmeters, one calibrated and within 1mV agreement with each other.

Also the following values (typically about 3.5% high across all values):

Set Voltage	Measured Voltage
3.0V	3.113V
2.7V	2.801V
2.1V	2.176V
1.8V	1.863V

RE: Excessively high output error (4%) with NPM1100

Sigurd Hellesvik — Tue, 09 Nov 2021 08:57:10 GMT

Hi Peter

I am still waiting for some more information on the VOUTB accuracy from our developers.

For the Battery Charger accuracy, have a look at the V_TERMACC0from the Charger Electrical parameters:

As you say, battery charging require good accuracy, so these are max +-1% in general and +-0.5% at 25 C.

For the VOUTB accuracy:

Do you measure this using the nPM1100-EK, or a custom board?

If you are going to use the Buck converter, will the 4% error here be an issue for your use-case?

Regards,
Sigurd Hellesvik

RE: Excessively high output error (4%) with NPM1100

peterqu94305 — Fri, 05 Nov 2021 16:23:21 GMT

Hello Siguard,

Thank you for looking into it. I have reviewed the graph showing the VOUTB accuracy across temperature range. Since we are testing this in our office, which is around 25 degree Celsius, the graph indicates the error should be closer to 0%. We have measured 4%.

Also for the termination voltage, the electrical parameters section in the datasheet only provided typical values, it did not provide min and max. We usually don't concern about these parameters too much. But in this case, we have measured 4% error across multiple NPM1100 and it made us to have real concern about all the parameters in the datasheet that do not have a min/max.

Typically termination voltage and output voltage shares the same bandgap reference circuit. It is plausible that there is a high error in the charging termination voltage. An incorrect charging termination voltage could leads to possibility of lithium ion cell explosion due to overcharging.

Thank you,
Peter

RE: Excessively high output error (4%) with NPM1100

Sigurd Hellesvik — Fri, 05 Nov 2021 13:53:45 GMT

Hi Peter

I see you found the Output accuracy.

Under Electrical Characteristics, there is also a graph showing VOUTB accuracy for different temperatures.

I will check with our developers how this relates to the accuracy limits, and return with a better answer by Tuesday.

For the Charging termination voltage accuracy, see these parameters.

Regards,
Sigurd Hellesvik

RE: Excessively high output error (4%) with NPM1100

peterqu94305 — Thu, 04 Nov 2021 15:39:20 GMT

Now that we have this issue, and after we read the datasheet carefully. Looks like the spec sheet states that the VOUTB accuracy is -2% to 8%.

This is type of error budget is unbelievable. A similar PMIC such as TI BQ24195 has +/-2% error.