Rtc (Optional); Schematic For The Crystal; Schematic For The External Crystal (Rtc) - Espressif Systems ESP32-C6 Series Hardware Design Manuallines

2 Schematic Checklist
11
MTDI
12
MTCK
13
MTDO
14
GPIO8
15
GPIO9
16
GPIO10
17
GPIO11
18
GPIO12
19
GPIO13
20
5
SPICS0
Notice:
• Defects in the manufacturing of crystal and oscillators (for example, large frequency deviation of more than ±10
ppm, unstable performance within operating temperature range, etc) may lead to the malfunction of ESP32-C6,
resulting in a decrease of the RF performance.
VDD33
• When Wi-Fi or Bluetooth connection fails, after ruling out software problems, you may measure the frequency
offset in 2.4 GHz via a radio communication analyzer or a spectrum analyzer and see if it is too large. If yes, adjust
capacitors at the two sides of the crystal to reduce frequency offset.

2.4.2 RTC (optional)

ESP32-C6 supports main crystal division, an external 32.768 kHz crystal, or an external signal e.g. an
oscillator to act as the RTC sleep clock, suitable for applications that require high-precision RTC clocks such as
4 8
scenario which requires the Bluetooth wake-up function.
GND VCC
Figure 8 shows the schematic for the external 32.768 kHz crystal.
Notice:
• Please note the requirements for the 32.768 kHz crystal.
– Equivalent series resistance (ESR) ⩽ 70 kΩ.
– Load capacitance at both ends should be configured according to the crystal's specification. For reference,
see Section 2.4.1.
• The parallel resistor R is used for biasing the crystal circuit (5 MΩ < R ⩽ 10 MΩ). In general, you do not need to
populate the resistor.
• If the RTC source is not required, then the pins for the external 32.768 kHz crystal can be used as GPIOs.
Espressif Systems
5
41
GND
40
VDDA2
39 R4
XTAL_P
38
XTAL_N
37
VDDA1
36
SDIO_DATA3
35
SDIO_DATA2
34
SDIO_DATA1
33
SDIO_DATA0
32
SDIO_CLK
31
SDIO_CMD
Figure 7: Schematic for the Crystal
The values of C1 and C4 vary with
the selection of the crystal.
The value of R4 varies with the actual
PCB board. The initial value could be
24 nH.
C2
10nF
GND
C13 TBD
GND
X1
32.768kHz
GND
C14 TBD
Figure 8: Schematic for the External Crystal (RTC)
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TBD
1
XIN
2
GND
4
GND
1
ANT
2
VDDA3P3
3
VDDA3P3
4
CHIP_EN
5
VDDPST1
GPIO0 6
XTAL_32K_P
GPIO1 7
XTAL_32K_N
8
GPIO2
9
GPIO3
10
MTMS
U1
12
ESP32-C6 Series Hardware Design Guidelines v1.0
4
4
GND
3
XOUT
GND
GND
Y1
C1
TBD
GND
40MHz(±10ppm)
3
GND
C4
TBD
R17 0
GND
C10
0.1uF
30
U0RXD
29 R3
U0TXD
28
VDDPST2
27
GPIO15
26 R16
SPID
25 R15
SPICLK
24 R14
SPIHD
23
VDD_SPI
22 R13
SPIWP
21
R10
SPIQ
C16
0.1uF
ESP32-C6
GND
3