Power Mode
Details
Mode Entry
Wake-Up Sources
Stop
• All internal power nets shut down
• 5V regulator remains active (if enabled)
• Internal 1.8 V LDO on
• Pins retain state
• Exit on any reset source
1. Clear STOPCF bit in
REG0CN
2. Set STOP bit in
PCON0
Any reset source
Snooze
• Core and peripheral clocks halted
• HFOSC0 and HFOSC1 oscillators stopped
• Regulators in low bias current mode for energy sav-
ings
• Timer 3 and 4 may clock from LFOSC0
• Code resumes execution on wake event
1. Switch SYSCLK to
HFOSC0
2. Set SNOOZE bit in
PCON1
• USB0 Bus Activity
• Timer 4 Event
• SPI0 Activity
• Port Match Event
• Comparator 0 Falling
Edge
• CLUn Interrupt-Enabled
Event
Shutdown
• All internal power nets shut down
• 5V regulator remains active (if enabled)
• Internal 1.8 V LDO off to save energy
• Pins retain state
• Exit on pin or power-on reset
1. Set STOPCF bit in
REG0CN
2. Set STOP bit in
PCON0
• RSTb pin reset
• Power-on reset
7.2 Features
The power management features of these devices include:
• Supports five power modes:
1. Normal mode: Core and all peripherals fully operational.
2. Idle mode: Core halted, peripherals fully operational, core waiting for interrupt to continue.
3. Suspend mode: High-frequency internal clocks halted, select peripherals active, waiting for wake signal to continue.
4. Snooze mode: High-frequency internal clocks halted, select peripherals active, regulators in low-power mode, waiting for wake
signal to continue.
5. Shutdown mode: All clocks stopped and internal LDO shut off, device waiting for POR or pin reset.
Note: Legacy 8051 Stop mode is also supported, but Suspend and Snooze offer more functionality with better power consumption.
• Internal Core LDO:
• Supplies power to majority of blocks.
• Low power consumption in Snooze mode, can be shut down completely in Shutdown mode.
• 5V-to-3.3V Regulator:
• Allows direct connection to USB supply net.
• Provides up to 100 mA for system-level use.
• Low power consumption in Snooze mode.
EFM8UB3 Reference Manual
Power Management and Internal Regulators
silabs.com
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