Can't achieve low power with PCA10028

[Lee Daniel Crocker]

I'm trying to measure absolute minimum power consumption of the chip using the PCA10028. I cut SB 9, and applied a very sensitive current measuring device to P22. I'm running the following code (no SD):

int main(void) {
    NRF_POWER->RAMON = POWER_RAMON_ONRAM0_RAM0On << POWER_RAMON_ONRAM0_Pos
                     | POWER_RAMON_ONRAM1_RAM1On << POWER_RAMON_ONRAM1_Pos
                     | POWER_RAMON_OFFRAM0_RAM0Off << POWER_RAMON_OFFRAM0_Pos
                     | POWER_RAMON_OFFRAM1_RAM1Off << POWER_RAMON_OFFRAM1_Pos;
    
    NRF_RADIO->TASKS_DISABLE = 1;
    NRF_POWER->TASKS_LOWPWR = 1;
    NRF_POWER->SYSTEMOFF = 1;
}

I'm consistently measuring 1.8 mA (that's milliamps--1000 times what the specsheet says I should be getting). I've read all the threads here, I'm pressing RESET (is there some other way I should be resetting the chip to get out of debug mode?), SYSTEMOFF mode says it powers down everything, so what am I missing?

Also, the signal I'm getting from the current measurement is jittery at about 3kHz. Is there maybe something on the board waking it up at that rate?

[Susheel Nuguru]

i am not sure if this would help, but i think there should be a while(1): in the end of the main function, else it will end up in hardfault handler.
Also i do not have the bitfield and product doc in hand, not sure what is going on with RAMON settings, are you switching it off or on? seems like your are doing both in one go?

[Lee Daniel Crocker]

Thanks, the while (1) {} didn't do it. The settings above I believe are both banks on when in ON mode and both off when in OFF mode. But even with the ram banks on, I shouldn't be getting a number this big. I'm not entirely sure I trust my measurements, so I'll investigate that for a while, but I don't think they're off by a factor of 1000.

[Susheel Nuguru]

Ah, i missed to see that there is no softdevice, it cannot be this high with power after system off as you have not started any clocks and you also made sure that the chip is in LOWPWR mode.

[Michael Dietz]

I wonder if its the interface MCU that is drawing this current. Have you eliminated the possibility of this? I'm really not sure about this so look into it yourself but I think the interface mcu makes it a bit difficult to measure current. it shares the same VCC with the nrf device and I think this is also in the current measure port. but if you look closely on the schematic you should be able to find a VCC_NRF or something like that on a pin out. and maybe try to measure there?

[Lee Daniel Crocker]

The PCA10028 has a specific current measurement port and very detailed instructions...cut a solder bridge, put in a 10 ohm resistor, measure across these two pins. I'm following that to the letter. Looks like I may just have to add some pins to my production board and measure it there.