Power state operation

Apart from transitions in or out of Shutdown state through the BUCKEN pin, all transitions between Sleep and Active states are automatic and do not rely on any control pin assertion or de-assertion.

Shutdown state is achieved by de-assertion on the BUCKEN pin. Asserting BUCKEN will result in the Active (IDLE sub-state) state being entered. The host will initiate the boot sequence through Serial Peripheral Interface (SPI)/Quad Serial Peripheral Interface (QSPI), culminating in the Sleep state being entered. This is the lowest power non-Shutdown state that can be achieved. Transitions from Active to Sleep are fully controlled by nRF7000. Transitions from Sleep to Active are determined by both the host and nRF7000. Sleep is entered opportunistically whenever there is no scan activity associated with a scan request from the host.

Transitioning from Shutdown or Sleep state to Active state involves the following steps:

1. Switch the Power Management Unit (PMU) to high power mode (Pulse-Width Modulation (PWM)).
2. Apply power to the digital logic, RAMs, and analog circuits.
3. Start the 40 MHz crystal oscillator and allow to settle.
4. Start the baseband PLL and allow to settle.
5. Boot all processor cores.
6. Execute baseband initializations.
7. Execute RF initializations and calibrations.

The initial steps consume equal duration whether originating in Shutdown or Sleep, while the baseband and RF initializations are dependent on the originating state. In particular:

• Full baseband initializations are required from Shutdown (including transferring the Factory Information Configuration Registers (FICR) information from One Time Programmable (OTP) memory into retention RAM), while in Sleep some of the state is retained in retention RAMs.
• Complete RF calibrations are required from Shutdown, including across channels to support scanning. From Sleep, only minimal initialization or calibration on the operating channel is required.

See Electrical specification for timing information.