NPM1300 high current draw

[robsrick]

Hi

I'm having an issue with my NPM1300. drawing high current. I've had 50 of these boards fabricated and the majority are fine, but with the same hw configuration, same fw i sometimes see high current draws of varying between 1 and 7mA.

I've narrowed it down to the NPM1300 in the following manner:

- First, i place the PPK2 in series with my battery and measure current during my BLE advertising state and get 1-7mA dependent on the board. On a good board i get 20uA.

- I then, one by one isolate VOUT1 and VOUT2 of the NPM1300 and place the ppk2 in series with all downstream circuitry. I see in the case of VOUT1 i get nanoamps which is expected, and in the case of VOUT2 i see 20uA which is expected because this is powering an NRF52840 which is advertising. 

I've included some screenshots from power profiler. the first shows a good board measured on the battery, the next two are examples of bad boards and the next two are isolating the vout1 and vout2 on a bad board.

Firstly, Do you agree in that case that it is likely the npm1300 is the cause?

and secondly do you have any ideas what might be causing such a high current draw?

I've included a snip of my schematics for the power supply, along with the layout.

below are the specs for the components in this part of the circuit:

1uF ±10% 10V X5R 0603

10uF ±10% 10V XS6 0603

L1 = Samsung CIGT201610EH2R2MNE

[dacr]

Hi Robert,

I see you supply LDO1 from VSYS, can you confirm there is no current load downstream from VOUTLDO1(3V0_C)?

Thanks,

Dan

[robsrick]

Hi Dan

Yes, good point i did check this. All downstream circuitry from 3V0_C is isolated by a 0ohm link which i removed to give the same results.

Regards

Robert

[dacr]

Thanks for confirming, I'm still trying to identify what could the issue be, and I'll get back to you with suggestions once I have them.

[dacr]

Hi Robert and peppershut,

It is possible that boards Vbatbad and Vbatbad2 suffer from different issues.

Firstly, can you indicate the markings on the nPM1300 package (maybe for the 3 boards: good, bad and bad2) to confirm what version of the nPM1300 you are using.

Secondly, can you confirm whether you applied the fix below on board Vbatbad2 (if applied on board Vbatbad, it is expected that you would not see any change)? If yes, can you please upload a new plot of the current on VBAT for this board, but with a zoom on the X-axis (around 500ms for the whole plot window) so that I get a clearer picture of the load profile.

&npm1300_ek_buck1 {
regulator-initial-mode = <NPM1300_BUCK_MODE_PFM>;
};

&npm1300_ek_buck2 {
regulator-initial-mode = <NPM1300_BUCK_MODE_PFM>;
};

Thirdly, for board Vbatbad, the behaviour seems to match errata #32, that unfortunately does not have a workaround, however it will be fixed in the next version of the nPM1300.

All the best,

Dan

[robsrick]

Hi Dan

Firstly, not sure who Peppershut is. Happy for them to participate of course but they're implying they are working on this project when they are not? strange.

Regarding your queries:

1) Part markings

VbatGood

Vbatbad1

vbatbad2

2) I'm fairly sure i applied the firmware change on VbatBad1 but i can't remember so here is the plots for both with the fix:

Vbatbad1 with firmware change (10s window)

Vbatbad1 with firmware change (500ms window centred on the ble adv. pulse)

Vbatbad2 with firmware change (10s window)

Vbatbad2 with firmware change (500ms window centred on the ble adv. pulse)

Vbatbad2 with firmware change (50ms window centred on the ble adv. pulse)

3) Looking at errata 32:

if this is the case, do you expect to see board to board variation for this errata? since some of my boards are okay and others are bad.

10% doesn't seem to match what I'm seeing, going from a typical 20uA current draw to 1mA isn't 10%.

I see errata 27 equates to around 1mA additional current draw which matches the case for vbatbad1 but i think your firmware change you suggested should resolve that if it was the case? Again, with this one would you expect board to board variation or does it apply to all boards?

Regards

Robert

[dacr]

Hi Robert,

Sorry for including peppershut, I just saw a comment from them and assumed it's the same project.

Yes, board variation is expected. No, the firmware change would not address this 1mA extra, it was just to remove the suspicion that either or both BUCKs were entering PWM mode hence the extra ~7mA current. So the proposed firmware change could potentially fix only board bad2, but from your findings it does not even do that.

It's interesting that the ~7mA extra is seen on a board with a different version. I will dig into that.

All the best,

Dan

[robsrick]

No problem, was just a bit confused!

Thanks for carrying on  digging into this.

Regards

Robert

[dacr]

Hi Robert,

Some more questions:

1. What is U13? Can you place a scope on VBUSIN to check for any activity there explaining the current consumption?
2. How do you configure GPIOs? Are any used as outputs? If so, can you place a scope on them to confirm there is no activity there to explain the extra current?
3. The version of the npm1300 you have no longer needs the Errata fix using the LOADSW, can you try to disable both LOADSW in firmware and see if it makes any changes?

All the best,

Dan