Can the nRF51822 be set up to run thr 32kHz clock in mode?
What is the lowest possible sleep current while maintaining BLE connection timing?
In system off mode, all clock sources and peripherals on the chip are turned off, and the only wakeup source is reset and pin change (for those that have this enabled). As given in table23 in the Product Specification, the current consumption in this mode is typical 0.4 µA without any RAM retention.
In section 8.1 of the S110 SoftDevice Specification, the current profile of the softdevice in different states are shown. In between connection events, the chip will be in system on, with the RTC running. Depending on whether you use a 32 kHz crystal or the internal RC oscillator, this gives a total consumption of I_on + I _RTC + I_X32k, typical 2.3 + 0.2 + 0.4 = 2.9 µA or i_on + I_RTC + I_RC32k = 2.3 + 0.2 + 0.8 = 3.3 µA.