Datasheet

16
11090BS–ATARM–22-Oct-13
SAM3S8/SD8 Summary
Figure 5-3. Backup Battery
5.4 Active Mode
Active mode is the normal running mode with the core clock running from the fast RC oscillator,
the main crystal oscillator or the PLLA. The power management controller can be used to adapt
the frequency and to disable the peripheral clocks.
5.5 Low-power Modes
The various low-power modes of the SAM3S8/SD8 are described below:
5.5.1 Backup Mode
The purpose of backup mode is to achieve the lowest power consumption possible in a system
which is performing periodic wake-ups to perform tasks but not requiring fast startup time
(<0.1ms). Total current consumption is 1.5 µA typical.
The Supply Controller, zero-power power-on reset, RTT, RTC, Backup registers and 32 kHz
oscillator (RC or crystal oscillator selected by software in the Supply Controller) are running. The
regulator and the core supply are off.
Backup mode is based on the Cortex-M3 deep sleep mode with the voltage regulator disabled.
The SAM3S8/SD8 can be awakened from this mode through WUP0-15 pins, the supply monitor
(SM), the RTT or RTC wake-up event.
Backup mode is entered by using WFE instructions with the SLEEPDEEP bit in the Cortex-M3
System Control Register set to 1. (See the Power management description in The ARM Cortex-
M3 Processor section of the product datasheet).
Exit from Backup mode happens if one of the following enable wake up events occurs:
• WKUPEN0-15 pins (level transition, configurable debouncing)
ADC, DAC
Analog Comp.
USB
Transceivers.
VDDIN
Voltage
Regulator
3.3V
LDO
Backup
Battery
+
-
ON/OFF
IN
OUT
VDDOUT
Main Supply
VDDCORE
ADC, DAC, Analog
Comparator Supply
(2.0V-3.6V)
VDDIO
VDDPLL
PIOx (Output)
WAKEUPx
External wakeup signal
Note: The two diodes provide a “switchover circuit” (for illustration purpose)
between the backup battery and the main supply when the system is put in
backup mode.