Power management- usuing external LFCLK

[Gili Elias]

Hi, I'm trying to reduce as much as I can the BLE current consumption in advertise mode and unfortunately I can't go under 1.6 mA. Can you please tell me what are the exact steps I should take to do that? What I want to do is to advertise with the defined interval on SYSTEM-ON base current with 16 kB RAM enabled. My current, as I understand it, should be around 2.6 uA, but I can't reach it.

I use an external Crystal LFCLK. How should I define the ble_stack_init? how should I define the timer_init and start_timer functions to use only in the LFCLK and not in HFCLK? For low current between advertises I use sd_app_evt_wait() function. Still, because of my stcak (probably) I can't reach the low current of 2.6 uA.

What's makes the current so high? What are the recommended settings to make the component work in minimum current?

Thanks.

[Ole Morten]

1.6 mA is way too high than you should have between connection events, so there's definitely something wrong. As you can see in the SDS, you should see I_on, I_RTC and either I_X32k or I_RC32k depending on clock source used. This should be about ~3 µA in total.

There are a couple of things that you should check when seeing problems like this:

• Make sure to power cycle the nRF51822 after debugging/programming, or else the debug interface will stay enabled, which consumes a lot of power.
• If you use the Evaluation Kit, make sure to disconnect/turn off the Segger. Depending on kit version, either turn off SW4 (2.0+) or remove jumpers on P8 (1.0).
• Make sure to disable all serial interfaces or other peripherals requiring the 16 MHz clock. Take a look at section 8.3 in the PS, as well as this question.

To use a 32 kHz crystal with the softdevice, all you have to do is pass the correct initialization parameter. Take a look at this question for examples.