nPM1100 - Current consumption is higher than expected

RE: nPM1100 - Current consumption is higher than expected

dossalab — Fri, 12 May 2023 09:22:10 GMT

I did some more measurements - this time using a separate 10 ohm shunt. It's a pretty rough measurement, but I finally see a proper consumption in the range of 10 uA without the load and 30-40 uA with the powered MCU.

So yes, using a regular multimeter is definitely not an option with such designs. Even with a proper setup that's still an interesting thing to consider - especially with lower-tier batteries with high internal resistance.

Thanks for your help and assistance!

RE: nPM1100 - Current consumption is higher than expected

Kenneth — Wed, 10 May 2023 09:37:51 GMT

Hello,

I suggest to order an PPK2 yes:
https://www.digikey.com/en/products/detail/nordic-semiconductor-asa/NRF-PPK2/13557476

Typically the in-rush current can be both rather high and short, because it can operate in mode that only turn on the regulator for a short periods of time (to save current), I can imagine that a resistor value of 10-100ohm can be problematic in that case (due to the voltage drop).

Kenneth

RE: nPM1100 - Current consumption is higher than expected

dossalab — Wed, 10 May 2023 09:03:33 GMT

Sorry for the late response - I tried to run some tests in the meantime and I think I might've found something.

I was measuring the current with a regular handheld multimeter, which (as it turns out) adds a very high shunt resistance while connected (something about 10 - 100 ohms, not sure exactly). This in turn seems to confuse the chip in various ways (for example it never starts the charger when the meter is in the circuit). That makes sense since that kind of shunt will create a rather large voltage drop which will make it impossible for the chip to monitor the charging process.

I used that setup because I already tried it before on simpler chips (i.e DC-DC converters) and it seemed to work fine.

So I need to find some better gear to continue measurements. I unfortunately do not have DK on my hands, so I can't confirm if it behaves the same in this setup.

I wonder what method of measuring power consumption is recommended? I know about PPK but I don't have it either. It was not obvious for me that a regular meter won't make a sensible measurement at such low currents.

RE: nPM1100 - Current consumption is higher than expected

Kenneth — Mon, 08 May 2023 10:58:52 GMT

Do you have access to an nPM1100-EK so you can measure on and try for comparison?
https://www.nordicsemi.com/Products/Development-hardware/nPM1100-EK

Unfortunately I am not able to find anything that can explain your behaviour, can you provide a measurement table with some voltage levels and the currents you measure?

Kenneth

RE: nPM1100 - Current consumption is higher than expected

dossalab — Fri, 05 May 2023 11:49:55 GMT

one more thing that I observed is that consumption seems to depend on battery level. I charged the battery overnight and now the chip is driving more (2.8 ma)

RE: nPM1100 - Current consumption is higher than expected

dossalab — Thu, 04 May 2023 14:17:58 GMT

I tried that and it doesn't seem to make a difference

RE: nPM1100 - Current consumption is higher than expected

Kenneth — Thu, 04 May 2023 13:46:26 GMT

Can you try to ground it for test?

Kenneth

RE: nPM1100 - Current consumption is higher than expected

dossalab — Thu, 04 May 2023 13:37:51 GMT

In my case I don't supply VBUS yet. I'm only measuring the consumption from the battery side. Though it's interesting that the current measurement match (i.e in the ticket you mentioned and in my case device consumes the same).

I don't see any voltage on VBUS when the design is powered. There is about 0.8 MOhm between VBUS and battery terminal when the battery is disconnected.

RE: nPM1100 - Current consumption is higher than expected

Kenneth — Thu, 04 May 2023 13:15:23 GMT

I found a similar case that I think explain it:
nPM1100. From were this current is coming?

Direct link:
RE: nPM1100. From were this current is coming?

Kenneth

RE: nPM1100 - Current consumption is higher than expected

dossalab — Thu, 04 May 2023 11:48:16 GMT

I only have 2 designs (the one that I mentioned at the beginning is just a standalone MCU to measure the firmware consumption - to make sure it's not affecting the test). I don't think I have a properly working nPM1100 design at my disposal.

All chips or parts that I have came from either Mouser or Digikey. All nPM1100 and inductors are from the same order (so I assume from the same batch)

Both of the designs use the same schematic component and library (so there may be issues, even though I'm not seeing em)

There doesn't seem to be other failures besides high current consumption. Charging and indications seem to work just fine.

One thing that maybe raises my brow is that reference layout has D3 and D4 pins (ship mode) disconnected (or maybe connected to inner layers?) In my design they are shorted to common ground.

Kicad symbols have a tendency to hide pins that have the same purpose (so that's why you don't see B2 pin, for example - however it's correctly connected on the board)

Overall the design is so simple I can't see any potential pitfalls here. Weird.

RE: nPM1100 - Current consumption is higher than expected

Kenneth — Thu, 04 May 2023 09:31:08 GMT

So from my understanding you have 3 layouts here, 1 that works and 2 the fails (do them fail or is the current just high). Could be interesting to compare them in more details (schematic and layout, possible also any voltages to see if they compare), I assume all designs are using the same revision of the nPM1100 here, what have you done with the pins not shown in your schematic?

Kenneth

RE: nPM1100 - Current consumption is higher than expected

dossalab — Thu, 04 May 2023 08:05:36 GMT

Since this board does not allow me to install that capacitor I've temporary switched to another board with slightly inferior layout but easier access to traces. So that's what I have so far:

All caps are X5R 10uF 6.3V (C1608X5R0J106M080AB). R12 is charge current selection, R1 is NTC stub. L1 is the main coil (DFE201210U)

The consumption is still around 2200 uA...

I'm not really sure where to look next. The chip is hand-soldered but I doubt something is shorted. I got pretty stable results with both lead-free and reballed leaded solder (with stable output voltage and working charger and indications)

There are no other components on this board besides the battery.

RE: nPM1100 - Current consumption is higher than expected

Kenneth — Wed, 03 May 2023 09:17:07 GMT

Hello,

I can't think of anything else either. Likely the regulator is not stable here.

Kenneth