Rtc Power Supply; Chip Power-Up And Reset Timing - Espressif Systems ESP32 Hardware Design Manuallines

Chapter 3. Schematic Checklist

3.1.3 RTC Power Supply

ESP32's VDD3P3_RTC pin is the RTC and analog power pin. It is recommended to place a 0.1 μF decoupling
capacitor near this power pin in the circuit.
Note that this power supply cannot be used as a single backup power supply.
The schematic for the RTC power supply pin is shown in Figure

3.2 Chip Power-up and Reset Timing

ESP32's CHIP_PU pin can enable the chip when it is high and reset the chip when it is low.
When ESP32 uses a 3.3 V system power supply, the power rails need some time to stabilize before CHIP_PU is
pulled up and the chip is enabled. Therefore, CHIP_PU needs to be asserted high after the 3.3 V rails have been
brought up.
To reset the chip, keep the reset voltage V
by external interferences, make the CHIP_PU trace as short as possible.
Figure ESP32 Power-up and Reset Timing
Table Description of Timing Parameters for Power-up and Reset
Table 1: Description of Timing Parameters for Power-up and Reset
Parameter Description
t Time reserved for the power rails to stabilize before the CHIP_PU
STBL
pin is pulled high to activate the chip
t Time reserved for CHIP_PU to stay below V
RST
chip
Espressif Systems
Fig. 7: ESP32 Schematic for RTC Power Supply Pin
in the range of (–0.3 ~ 0.25 × VDD) V. To avoid reboots caused
IL_nRST
shows the power-up and reset timing of ESP32.
Fig. 8: ESP32 Power-up and Reset Timing
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ESP32 Schematic for RTC Power Supply
provides the specific timing requirements.
to reset the
IL_nRST
Pin.
Minimum (µs)
50
50
Release master