Schematic For The Crystal - Espressif Systems ESP32-H2 Series Hardware Design Manuallines

2 Schematic Checklist
Crystal
The circuit for the crystal is shown in Figure 5. Note that the accuracy of the selected crystal should be within
±10 ppm.
Please add a series component (resistor or inductor, see R4 in Figure 5) on the XTAL_P clock trace. Initially, it is
suggested to use an inductor of 24 nH to reduce the impact of high-frequency crystal harmonics on RF
performance, and the value should be adjusted after an overall test.
The initial values of external capacitors C1 and C4 can be determined according to the formula:
where the value of C
the PCB's stray capacitance. The values of C1 and C4 need to be further adjusted after an overall test as
below:
1. Select TX tone mode using the
2. Observe the 2.4 GHz signals with a radio communication analyzer or a spectrum analyzer and demodulate
it to obtain the actual frequency offset.
3. Adjust the frequency offset to be within ±10 ppm (recommended) by adjusting the external load
capacitance.
• When the center frequency offset is positive, it means that the equivalent load capacitance is small,
and the external load capacitance needs to be increased.
• When the center frequency offset is negative, it means the equivalent load capacitance is large, and
the external load capacitance needs to be reduced.
• External load capacitance at the two sides are usually equal, but in special cases, they may have
slightly different values.
9
VDDPST1
10
GPIO8
11
GPIO9
12
GPIO10
13
GPIO11
14
GPIO12
15
XTAL_32K_P
16
XTAL_32K_N
Notice:
• Defects in the manufacturing of crystal (for example, large frequency deviation of more than ±10 ppm, unstable
performance within operating temperature range, etc) may lead to the malfunction of ESP32-H2, resulting in a
decrease of the RF performance.
• It is recommended that the amplitude of the crystal is greater than 500 mV.
Espressif Systems
C
(load capacitance) can be found in the crystal's datasheet, and the value of C
L
Certification and Test
33
GND
32
ANT
31
VDD3P3
30
VDD3P3
29 R4
XTAL_P
28
XTAL_N
27
VDD3P3
26
GPIO27
25
GPIO26
Figure 5: Schematic for the Crystal
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C1 × C4
= + C
L stray
C1 + C4
Tool.
TBD
1
XIN
2
GND
10
4
GND
3
XOUT
ESP32-H2 Series Hardware Design Guidelines v0.5
refers to
stray