Datasheet

39
ATmega169A/PA/329A/PA/649A/P/3290A/PA/6490A/P [DATASHEET]
8284E–AVR–02/2013
10. Power management and sleep modes
10.1 Overview
Sleep modes enable the application to shut down unused modules in the MCU, thereby savingpower. The AVR
provides various sleep modes allowing the user to tailor the power consumption to the application’s requirements.
10.2 Sleep modes
Figure 9-1 on page 29 presents the different clock systems in the Atmel
ATmega169A/169PA/329A/329PA/3290A/3290PA/649A/649P/6490A/6490P, and their distribution. The figure is
helpful in selecting an appropriate sleep mode. Table 10-1 shows the different sleep modes and their wake up
sources and BOD disable ability
(1)
.
Note: 1. BOD disable is only available for ATmega169PA/329PA/3290PA/6490P.
Notes: 1. Only recommended with external XTAL or resonator selected as clock source.
2. If either LCD controller or Timer/Counter2 is running in asynchronous mode.
3. For INT0, only level interrupt.
To enter any of the sleep modes, the SE bit in SMCR must be written to logic one and a SLEEP instruction must be
executed. The SM2, SM1, and SM0 bits in the SMCR Register select which sleep mode will be activated by the
SLEEP instruction. See Table 10-2 on page 44 for a summary.
If an enabled interrupt occurs while the MCU is in a sleep mode, the MCU wakes up. The MCU is then halted for
four cycles in addition to the start-up time, executes the interrupt routine, and resumes execution from the instruc-
tion following SLEEP. The contents of the Register File and SRAM are unaltered when the device wakes up from
sleep. If a reset occurs during sleep mode, the MCU wakes up and executes from the Reset Vector.
10.3 BOD disable
(1)
When the Brown-out Detector (BOD) is enabled by BODLEVEL fuses - see Table 28-4 on page 295 and onwards,
the BOD is actively monitoring the power supply voltage during a sleep period. To save power, it is possible to dis-
able the BOD by software for some of the sleepmodes, see Table 10-1 on page 39. The sleep mode power
consumption will then be at the same level as when BOD is globally disabled by fuses. If BOD is disabled in soft-
ware, the BOD function is turned off immediately after entering the sleep mode. Upon wake-up from sleep, BOD is
automatically enabled again. This ensures safe operation in case the VCC level has dropped during the sleep
period.
Table 10-1. Active clock domains and wake-up sources in the different sleep modes.
Sleep Mode
Active Clock Domains Oscillators Wake-up Sources
Software BOD Disable clk
CPU
clk
FLASH
clk
IO
clk
ADC
clk
ASY
Main Clock Source Enabled Timer Osc Enabled INT0 and Pin Change USI Start Condition LCD Controller Timer2 SPM/ EEPROM Ready ADC Other I/O
Idle XXXXX
(2)
XXXXXXX
ADC NRM X X X X
(2)
X
(3)
XX
(2)
X
(2)
XX
Power-down X
(3)
XX
Power-save X X X
(3)
XXX X
Standby
(1)
XX
(3)
XX