Espressif ESP32 Technical Reference Manual page 691

31 Low-Power Management (RTC_CNTL)
31.3.1 Overview
The low-power management unit includes voltage regulators, a power controller, power switch cells, power do-
main isolation cells, etc. Figure
31.3.2 Digital Core Voltage Regulator
The built-in voltage regulator can convert the external power supply (typically 3.3V) to 1.1V to support the internal
digital core. It receives a wide range of external power supply from 1.8V to 3.6V, and provides an output voltage
from 0.90V to 1.25V.
1. When XPD_DIG_REG == 1, the regulator outputs a 1.1V voltage and the digital core is able to run; when
XPD_DIG_REG == 0, both the regulator and the digital core stop running.
2. DIG_REG_DBIAS[2:0] tunes the supply voltage of the digital core:
3. The current to the digital core comes from pin VDD3P3_CPU and pin VDD3P3_RTC.
Figure 31-2 shows the structure of a digital core's voltage regulator.
31.3.3 Low-Power Voltage Regulator
The built-in low-power voltage regulator can convert the external power supply (typically 3.3V) to 1.1V to support
the internal RTC core. To save power, it receives a wide range of external power supply from 1.8V to 3.6V, and
supports an adjustable output voltage of 0.90V to 1.25V in normal work mode, a fixed output voltage of about
0.75V both in Deep-sleep mode and Hibernation mode.
1. When the pin CHIP_PU is at a high level, the low-power voltage regulator cannot be turned off. It should
be switched only between normal-work mode and Deep-sleep mode.
Espressif Systems
31-1 shows the high-level architecture of ESP32's low-power management.
VDD_DIG = 0.90 + DBIAS · 0.05V
Figure 31-2. Digital Core Voltage Regulator
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ESP32 TRM (Version 5.2)