35uA ship mode current with NM1300

[vielleicht]

Hi there,

I built a battery powered custom PCBA with the NRF54L15 and the nPM1300. All the configuration and register work via I2C seems to be working properly (reading V_BAT, T_NTC, controlling LED2 and LDSW via host). I'm currently running the PCBA on a PPK2 to evaluate current consumption. On normal run the system takes 700uA when shipmode is grounded (only 50k internal pullup) by wake sensor and 470uA, when wake sensor is not triggering. Not the best results, but for the first shot ok.

When the nPM enters shipmode (via I2C), the current consumption only falls to 35uA (not the expected 350nA). I checked the measurement with the nPM1300-ek, which gave me correct measurement values of about 350nA in ship mode (with some spikes every 2s).

Now, I do not know, what I am doing wrong. Here are the last commands via I2C when entering ship mode (taken by an oscilloscope on the I2C lines):

Packet;Start Time;End Time;Address Bits;Address;Address + R/W;R/W;Address ACK;Data;Data ACK
1;-1,04983682155295E-05;0,000419069619635458;7;6B;D6;Write;0;08 00 01;0 0 0
2;0,000456957618563912;0,000799485608876558;7;6B;D6;Write;0;08 04;0 0
3;0,000799485608876558;0,00101913360266449;7;6B;D7;Read;0;10;1
4;0,00893004537892862;0,00935910136679409;7;6B;D6;Write;0;08 01 01;0 0 0
5;0,00939391736580942;0,00973593335613655;7;6B;D6;Write;0;08 04;0 0
6;0,00973593335613655;0,00995506934993896;7;6B;D7;Read;0;00;1
7;0,0100252133479552;0,0103682533382533;7;6B;D6;Write;0;05 11;0 0
8;0,0103682533382533;0,0105879013320412;7;6B;D7;Read;0;9B;1
9;0,0106216933310855;0,0109631973214272;7;6B;D6;Write;0;05 12;0 0
10;0,0109631973214272;0,0111828453152151;7;6B;D7;Read;0;E9;1
11;0,0112591333130575;0,011688189300923;7;6B;D6;Write;0;05 00 01;0 0 0
12;0,0117240292999094;0,0121530852877748;7;6B;D6;Write;0;05 01 01;0 0 0
13;0,0123619812818668;0,0127910372697323;7;6B;D6;Write;0;0B 02 01;0 0 0

In short, in the end there's a write of three bytes: 0B 02 01 (2bytes TASKENTERSHIPMODE, 1 byte TRIGGER)

The behavior changes like expected (VDD discharges slowly), but consumptions stays to high.

Additionally here's a small cutout from the schematic (don't want to disclose too much details):

The 2 coin-cell batteries (or in this case the PPM2) are only connected to the VBAT (VDD_BAT net in the schematic). No capacitor, resistor or any other componets are connected.

I really cannot figure out, what the issue could be. Am I missing some configuration?

[Asbjørn]

Hello Philipp,

from your description it sounds like there's one or possible two GPIOs leaking current when you enable ship mode. First I'd check would be I2C interface itself it that could be left leaking or if the pull up on those lines are not the expected values? If this doesn't get you anywhere closer, I'd have a look at the other GPIOs on the nRF54L15 when you enter ship mode. Could one of them be left floating when VDD is dropped from the nPPM1300?

Best regards

Asbjørn

[vielleicht]

Ah, sorry, I didn't tell you that VDD of the nRF54x is connected to VOUT1, which should be cut down in sleep. All components are connected to the VDD. Only the nPM is connected to VBAT.

Here's the voltages on nPM1300 pins:

1 (VOUT1): 780mV

3 (SW1): 780mV

4 (VSYS): 518mV

12 (VDDIO): 430mV

13 (SDA): 430mV

14 (SCL): 430mV

17: 0mV

18 (NTC): 0mV

19 (VBAT): 3000mV

20 (VSYS): 510mV

21 (VDD_CHG): 0mV

25 (LED): 0mV

26 (LED): 1400mV eff (some pulsing voltage with capacity)

27 (LED): 0mV

others are also 0mV

I thought, in ship mode, VOUT1 and VDDIO would be 0V? did I miss-configure anything? or are there any recommendations for reaching the 370nA sleep?

[vielleicht]

I now removed the SDA and SCL pull-ups to VDDIO, but ship-current still is 38µA. 780mV are still valid. Any assistance appreciated!

[runsiv]

Hi and thank you for your patience. Asbjørn is out of office this week so I will start looking into it

Regards

Runar

[runsiv]

Hi, 

How is the SHPHLD pin connected? 

Regards

Runar

[vielleicht]

Now you pointed it out! This was the hint. For debugging purposes, I connected the SHPHLD not only to the wake sensor, but also to a GPIO of the µC. I missed it up to now, because I thought the µC is without supply and therefore should not draw current. But it obviously does due to internal circuit.

We are now down to 400nA with a quiescent current of 30nA of the Power Profiler. Should be enough fine.

There still are spikes of 47µA every 2.5s. Is this intentional? Though, I doesn't look like its drawing to much charge due to the short duration of the spike.