Clock source, power consumption in sleep mode

[arikramon]

I am using nRF52832 SDK 15.2.

I would like to avoid using the 32.768kHz oscillator to save space and cost.

I am using BLE and sleep mode ON.

I defined in sdk_config.h the following:

  1. #define CLOCK_CONFIG_LF_SRC  0 (source RC)

  2. #define NRF_SDH_CLOCK_LF_SRC  2 (source SYNTH)

I noticed that in sleep mode OFF the current consumption is less then 2uA which is OK, but in sleep mode ON the power consumption is 610uA.

My questions are:

1. Can BLE work with the SYNTH clock?

2. Is the power consumption in sleep mode ON is as expected or I should expect less then 610uA ?

Thanks

[Simonr]

Hi Arik

1. Yes, but synthesizing the 32.768 kHz clock only makes sense if the external 16MHz crystal is running, and you'll have to start that before enabling the LF clock in this instance. The RC clock will be a much better option to achieve a longer battery life in this instance.

2. Does the 610uA occur when using the RC clock as well? Because that should not be the case in System ON mode unless you're using a TIMER to wake up the device. Using the RTC would be a better option, as it uses the LFCLK and not the HFCLK.

When using the synthesized LF clock an HF clock will be running at all times which will use 250-470uA depending on the usage. I assume there is a peripheral/timer that isn't uninitialized properly that's causing the 610uA current consumption.

Due to the summer holidays in Norway, our support team is understaffed this week, and delayed replies must be expected. Sorry for the inconvenience!

Best regards,

Simon

[arikramon]

Thanks Simon

Regarding answer #2: I enter sleep mode in order to wake up by a timer using xTaskNotifyWait.

Is there a better way of doing it?

thanks

Arik