Rtc Clock (Optional) - Espressif Systems ESP32-C3FH4 Hardware Design Manuallines

2 Schematic Checklist
VDD33
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Notice:
• If you use an oscillator, its output should be connected to XTAL_P on the chip through a series inductor
(initially of 20 nH). XTAL_N can be floating. Please make sure that the oscillator output is stable and
its accuracy is within ±10 ppm. It is also recommended that the circuit design for the oscillator is
compatible with the use of crystal, in case that if there is a problem with oscillator circuit, the oscillator
can be replaced by the crystal.
• Although ESP32-C3 family has calibration circuits, defects in the crystal itself (for example, large fre-
quency deviation of more than ±10 ppm, unstable performance over operating temperature range, etc)
may lead to the malfunction of ESP32-C3 family, resulting in RF performance degradation.

2.4.2 RTC Clock (optional)

ESP32-C3 family supports an external 32.768 kHz crystal to act as the RTC sleep clock.
Figure 8 shows the schematic for the external 32.768 kHz crystal.
Notice:
• 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.
• The parallel resistor R10 is used for biasing the crystal circuit (5 MΩ < R12 ⩽ 10 MΩ). In general, you
do not need to populate R10.
• If the RTC source is not required, then pin 4 (XTAL_32K_P) and pin 5 (XTAL_32K_N) can be used as
general GPIOs.
Espressif Systems
4
R1 0
1
C1
10nF
GND
Figure 7: Schematic for ESP32­C3 Family's Oscillator
Figure 8: Schematic for ESP32­C3 Family's External Crystal (RTC)
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Y1
3
VCC OUT
2
NC GND
40MHz(±10ppm)
GND
4
10
TBD
XTAL_P
L3
ESP32-C3 Family Hardware Design Guidelines V1.0
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