Clock Source; External Clock Source (Compulsory) - Espressif Systems ESP32-C3FH4 Hardware Design Manuallines

2 Schematic Checklist
SPIQ
SPID
SPICLK
SPICS0
SPIWP SPIWP
SPIHD
VDD_SPI
VDD3P3_CPU
ESP32-C3

2.4 Clock Source

There are two clock sources for ESP32-C3 family, namely an external crystal clock source and an RTC clock
source.

2.4.1 External Clock Source (compulsory)

Currently, the ESP32-C3 family firmware only supports 40 MHz crystal. The specific capacitance of C1 and C2
depends on further testing of, and adjustment to, the overall performance of the whole circuit. Please add a
component in series on the XTAL_P clock trace to reduce the drive capability of the crystal and to minimize the
TBD
3 L3
impact of crystal harmonics on RF performance. The value of this component (initially of 24 nH) depends on
2
further testing. Note that the accuracy of the selected crystal needs to be ±10 ppm.
GND
Espressif Systems
24 R3 0 SPIQ
23 R4 0 SPID
22 SPICLK
R5 0
21 SPICS0
20 R6 0 SPIWP
19 19 R7 R7 0 0 SPIHD SPIHD
18
VDD_SPI
17
C10 C11
0.1uF 1uF
GND GND
Figure 5: ESP32­C3 Family Flash Circuit
C12
0.1uF
GND
XTAL_P
33
GND
32
VDDA
31
VDDA
30
R1
XTAL_P
29
XTAL_N
28
U0TXD
27
3
U0RXD
26
GPIO19
25
GPIO18
Figure 6: Schematic for ESP32­C3 Family's Crystal
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SPICS0
SPICLK
SPIHD
VDD33
VDD33
If using ESP32-C3FN4 or ESP32-C3FH4,
external flash could be removed.
0
1
XIN
2
GND XOUT
9
ESP32-C3 Family Hardware Design Guidelines V1.0
VDD_SPI
1 5
/CS /CS DI DI
6 2
CLK DO
7 3
/HOLD /WP
U3 FLASH-3V3
GND
4
2
GND
3
SPID
SPIQ
SPIWP
1