Analog Power Supply; Power-On Sequence And System Reset; Power-On Sequence; Reset - Espressif Systems ESP32 Series Hardware Design Manuallines

2. Schematic Checklist and PCB Layout Design

2.1.1.2 Analog Power Supply

Pin1, pin3, pin4, pin43 and pin46 are the analog power supply pins. It should be noted that the sudden increase
in current draw, when ESP32 is in transmission mode, may cause a power rail collapse. Therefore, it is highly
recommended to add another 10 µF capacitor to the power trace, which can work in conjunction with the 0.1 µF
capacitor. LC filter circuit needs to be added near the power pin so as to suppress high-frequency harmonics.
The inductor's rated current is preferably 500 mA and above.
VDD33
VDD33
VDD33
ANT1
PCB ANT
Notice:
• The recommended voltage of the power supply for ESP32 is 3.3 V, and its recommended output current is 500 mA
or more.
• It is suggested that users add an ESD tube at the power entrance.

2.1.2 Power-on Sequence and System Reset

2.1.2.1 Power-on Sequence

ESP32 uses a 3.3 V system power supply. The chip should be activated after the power rails have stabilized. This
is achieved by delaying the activation of CHIP_PU (Pin9) after the 3.3 V rails have been brought up. More details
can be found in section Power Scheme in
Notice:
If CHIP_PU is driven by a power management chip, then the power management chip controls the ESP32 power
state. When the power management chip turns on/off Wi-Fi through the high/low level on GPIO, a pulse current
may be generated. To avoid level instability on CHIP_PU, an RC delay circuit is required.

2.1.2.2 Reset

CHIP_PU serves as the reset pin of ESP32. The input level (V
and remain so for a period of time. More details can be found in section Power Scheme in
Espressif Systems
C3
100pF
GND
L5
C13 C12 C11 C10
10uF NC 1uF 0.1uF
GND GND GND GND
1 L4 TBD
2
C15 C14
C16
TBD TBD
270pF(NC)
Figure 3: ESP32 Analog Power Supply Pins
270pF(NC)
GND GND GND
C17
ESP32 Datasheet.
The capacitance of C1 and C2 varies
with the selection of the crystal.
C20
GND
1uF
R1
C5 C6
GND
10nF/6.3V(10%)
3.3nF/6.3V(10%)
C9
GND
0.1uF
GND
2.0nH
C21
NC
GND
1
VDDA
2
LNA_IN
3
VDD3P3
4
VDD3P3
SENSOR_VP 5
SENSOR_VP
6
SENSOR_CAPP
7
SENSOR_CAPN
SENSOR_VN 8
SENSOR_VN
CHIP_PU 9
CHIP_PU
GPIO34 10
VDET_1
GPIO35 11
VDET_2
GPIO32 12
32K_XP
GPIO33 13
32K_XN
GPIO25 14
GPIO25
U2
) for resetting the chip should be low enough
IL_nRST
4 ESP32 Hardware Design Guidelines V2.7
GND
GND
U1
C1
TBD
20K(5%)
R2
GND
0R 40MHz+/-10ppm
R3 499R
VDD3P3_CPU
SD_DATA_1
SD_DATA_0
SD_DATA_3
SD_DATA_2
VDD_SDIO
ESP32-D0WD
ESP32 Datasheet.
GND
C2
TBD
GPIO
U0TX
U0RX
GPIO
GND
C4
V
0.1uF
38 GPIO
GPIO19
37
36 GPIO
GPIO23
35 GPIO
GPIO18
34 GPIO
GPIO5
33 SDI/S
32 SDO/S
31 SCK/C
SD_CLK
30
SCS/C
SD_CMD
29 SWP/
28 SHD/S
27 GPIO
GPIO17
26
25 GPIO
GPIO16
C18
VD
1uF
GND
V
C19
0.1uF
GND