AT91SAM datasheet(21/67 Pages) ATMEL

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11100BS–ATARM–31-Jul-12

SAM4S Series [Preliminary]

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 SAM4S 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. Total

current consumption is 1 µA typical (VDDIO = 1.8V to 25°C).

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-M4 deep sleep mode with the voltage regulator disabled.

The SAM4S 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 writing the Supply Controller Control Register (SUPC_CR) with the

VROFF bit at 1 (a key is needed to write the VROFF bit, please refer to the “Supply Controller

(SUPC)” section of the product datasheet) and with the SLEEPDEEP bit in the Cortex-M4 Sys-

tem Control Register set to 1. (See the Power management description in the “ARM Cortex-M4

Processor” section of the product datasheet).

ADC, DAC

Analog Comp.

USB

Transceivers.

VDDIN

Voltage

Regulator

3.3V

LDO

Backup

Battery

ON/OFF

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.

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