Power, Reset, and Clock Management
8.1.4.3.3 Deepsleep1
DeepSleep1 mode enables lower power consumption than Standby mode. The main characteristic of this
mode which distinguish it from Standby mode is the main oscillator (OSC0) is disabled.
DeepSleep1 is the lowest sleep mode required for certain USB wakeup modes. See
,
Supported Low Power USB Wakeup Scenarios, for more information.
Further power reduction can be achieved in this mode if the RTC function is not required. See
, Internal RTC LDO.
Similar to Standby mode, the contents of the internal SRAM are lost because PD_MPU is turned OFF. In
addition, the contents of the SDRAM are preserved by placing the SDRAM in self-refresh. Activity on
wakeup peripherals via wake-up events enables the master crystal oscillator using the oscillator control
circuit. The wakeup events also interrupt CortexM3. See
, Wakeup Sources/Events, for
details on wakeup sources.
8.1.4.3.4 Deepsleep0
DeepSleep0 mode enables lower power consumption than DeepSleep1. The main characteristics of the
mode which distinguish it from other higher power modes are:
•
All on-chip power domains are shut off (except PD_WKUP and PD_RTC remain ON) to reduce power
leakage
•
VDD_CORE power (except VDDA analog) to DPLLs is turned OFF using dpll_pwr_sw_ctrl register (PG
2.x only)
•
VDDS_SRAM_CORE_BG is in retention using SMA2.vsldo_core_auto_ramp_en (PG2.x only)
DeepSleep0 mode is typically used during periods of inactivity when the user requires very low power
while waiting for an event that requires processing or higher performance. This is the lowest power mode
which still includes DDR in self-refresh, so wakeup events do not require a full cold boot, which greatly
reduces wakeup latencies over RTC-only mode.
Further power reduction can be achieved in this mode if the RTC function is not required. See
, Internal RTC LDO.
Before entering DeepSleep0 mode, peripheral and MPU context must be saved in the DDR. Upon
wakeup, the boot ROM executes and checks to see if it has resumed from a DeepSleep0 state. If so, it
redirects to the DDR to continue the resume process. Because power to PD_WKUP is ON throughout
DeepSleep0, power to key modules such as GPIO0, I2C, and others is maintained to allow wakeup events
to exit out of this mode. In addition, power to OCMC RAM is maintained to preserve information internally
during DeepSleep0.
Activity on wakeup peripherals via wakeup events enables the master crystal oscillator using the oscillator
control circuit. The wakeup events also interrupt CortexM3 which controls proper enabling of power
domains and clocks in the PRCM. See
, Wakeup Sources/Events, for details on wakeup
sources during DeepSleep0 and other low power modes mentioned.
8.1.4.3.5 RTC-Only
RTC-only mode is an ultra-low power mode which allows the user to maintain power and clocks to the
real-time clock (RTC) domain while the rest of the device is powered down. All context and memories will
be lost, and the only portion of the chip that will be maintained is the RTC. Only the RTC power supply
must be ON. All the remaining supplies must be OFF. The RTC battery backup domain consists of the
RTC subsystem (RTCSS), a dedicated, on-chip 32.768 Hz crystal oscillator and I/Os associated with the
RTCSS: pmic_power_en and ext_wakeup.
gives a high level view of system which implements the RTC-only mode.
511
SPRUH73H – October 2011 – Revised April 2013
Power, Reset, and Clock Management (PRCM)
Copyright © 2011–2013, Texas Instruments Incorporated