Please read datasheet page16--
13.1.4 QPU_Off state
The QPU_Off state is a higher power consumption off mode, in which all internal circuitry
required for a power on is biased and ready to start a power up sequence.
If LPM_OFF = 1 and no turn on event is present, the device stops at the QPU_Off state,
and waits until a valid turn on event is present.
In this state, if VDDIO supply is provided externally, the device is able to communicate
through I2C to access and modify the mirror registers in order to operate the device in
TBB mode or to program the OTP registers as described in Section 17 "OTP/TBB and