RE: Custom board with external crystal is consuming too much power when powered down

abvio — Sun, 20 Nov 2022 16:14:12 GMT

Thanks so much for your advice, Einar. You were right. The circuit board was leaving a 3V signal on on the display, and even though the 5V VDD was powered down, the signal was drawing the extra current. After a little redesigning, the circuit is now consuming < 1 uA. The Bluetooth modules were also damaged by overheated during reflow, which confused me a bit, but your original advice helped me narrow in on the actual problem.

Steve

RE: Custom board with external crystal is consuming too much power when powered down

Einar Thorsrud — Thu, 10 Nov 2022 12:45:51 GMT

Hi,

As long as the device stays in system off mode, the current consumption should be very low (in the order of 1 uA). However, there could be other parts of your board that contributes to the current consumption. Could that be the case? Another thing to check is the state of your GPIOs. These will retain the state when entering system off mode, so for instance an output pin set to high or low will still be in that state in system off mode. Therefor, there is a need to do a bit of clean-up before entering system off mode.

[quote user=""]Any thoughts on how I can assure that the external crystal is being used for the clock and reduce power draw during sleep?[/quote]

Even the LF clock is turned off in system OFF sleep mode (it is enabled in the system ON sleep mode though, which is the "normal" sleep mode). So that is not the case here. Regardless, in your config you have CONFIG_CLOCK_CONTROL_NRF_K32SRC_XTAL=y, so you are using the crystal (when the clock is running).