3. FUNCTIONAL DESCRIPTION
3.4 RTC and Low-Power Management
With the use of advanced power management technologies, ESP32 can switch between different power modes
(see Table
).
•
Power modes
–
Active mode: The chip radio is powered on. The chip can receive, transmit, or listen.
–
Modem-sleep mode: The CPU is operational and the clock is configurable. The Wi-Fi base- band and
radio are disabled.
–
Light-sleep mode: The CPU is paused. The RTC memory and RTC peripherals, as well as the ULP
co-processor are running. Any wake-up events (MAC, host, RTC timer, or external interrupts) will wake
up the chip.
–
Deep-sleep mode: Only the RTC memory and RTC peripherals are powered on. Wi-Fi connection
data are stored in the RTC memory. The ULP co-processor can work.
–
Hibernation mode: The internal 8-MHz oscillator and ULP co-processor are disabled. The RTC recovery
memory is powered down. Only one RTC timer on the slow clock and some RTC GPIOs are active.
The RTC timer or the RTC GPIOs can wake up the chip from the Hibernation mode.
•
Sleep Patterns
–
Association sleep pattern: The power mode switches between the Active mode, Modem- and Light-
sleep mode during this sleep pattern. The CPU, Wi-Fi and radio are woken up at predeter- mined
intervals to keep Wi-Fi connections alive.
–
ULP sensor-monitored pattern: The main CPU is in the Deep-sleep mode. The ULP co-processor takes
sensor measurements and wakes up the main system, based on the data collected from sensors.
Table 5: Functionalities Depending on the Power Modes
Power mode
Active
Modem-sleep Light-sleep
Deep-sleep
Hibernation
Sleep pattern
Association sleep pattern
ULP
sensor-
monitored pattern
-
CPU
ON
ON
PAUSE
OFF
OFF
Wi-Fi baseband and radio
ON
OFF
OFF
OFF
OFF
RTC memory and RTC pe-
ripherals
ON
ON
ON
ON
OFF
ULP co-processor
ON
ON
ON
ON/OFF
OFF
The power consumption varies with different power modes/sleep patterns and work statuses of functional modules.
Please see Table
for details.
Table 6: Power Consumption by Power Modes
Power mode
Description
Power consumption
Active (RF working)
Wi-Fi Tx packet 14 dBm
~
19.5 dBm
Wi-Fi Tx packet 0 dBm
Wi-Fi Rx and listening
Association sleep pattern (by Light-sleep)
1 mA
~
4 mA @DTIM3
