Product Specs

Table Of Contents
18 POWER Power supply
Page
79
POWER
REG
Supply
VDD
1.3V System power
DCC
DEC4
GND
DC/DC
LDO
DCDCEN
Figure 14: DC/DC regulator setup
18.2 System OFF mode
System OFF is the deepest power saving mode the system can enter. In this mode, the system’s core
functionality is powered down and all ongoing tasks are terminated.
The device can be put into System OFF mode using the POWER register interface. When in System OFF
mode, the device can be woken up through one of the following signals:
1. The DETECT signal, optionally generated by the GPIO peripheral
2. The ANADETECT signal, optionally generated by the LPCOMP module
3. The SENSE signal, optionally generated by the NFC module to wake-on-field”
4. A reset
When the system wakes up from System OFF mode, it gets reset. For more details, see Reset behavior on
page 83.
One or more RAM sections can be retained in System OFF mode depending on the settings in the
RAM[n].POWER registers.
RAM[n].POWER are retained registers, see Reset behavior. Note that these registers are usually overwritten
by the startup code provided with the nRF application examples.
Before entering System OFF mode, the user must make sure that all on-going EasyDMA transactions have
been completed. This is usually accomplished by making sure that the EasyDMA enabled peripheral is not
active when entering System OFF.
18.2.1 Emulated System OFF mode
If the device is in debug interface mode, System OFF will be emulated to secure that all required resources
needed for debugging are available during System OFF.
See Debug and trace on page 72 for more information. Required resources needed for debugging include
the following key components: Debug and trace on page 72, CLOCK Clock control on page 101,
POWER Power supply on page 78, NVMC Non-volatile memory controller on page 29, CPU, Flash,
and RAM. Since the CPU is kept on in an emulated System OFF mode, it is recommended to add an infinite
loop directly after entering System OFF, to prevent the CPU from executing code that normally should not be
executed.