ESPRESSIF SYSTEMS PTE LTD ESPWROOMS2 ユーザーズマニュアル
3. Functional Description
3.3.
Crystal Oscillator
ESP-WROOM-S2 uses 26 MHz crystal oscillator. The accuracy of the crystal oscillator
should be ±10 PPM, and the operating temperature range is -20°C to 85°C.
should be ±10 PPM, and the operating temperature range is -20°C to 85°C.
When using the download tool, please note to select the right crystal oscillator type. In
circuit design, capacitors C1 and C2 which connect to the earth, are added to the input
and output terminals of the crystal oscillator respectively. The values of the two capacitors
can be flexible, ranging from 6 pF to 22 pF, however, the specific capacitive values depend
on further testing and adjustment on the overall performance of the whole circuit. Normally,
the capacitive values of C1 and C2 are within 10 pF for the 26 MHz crystal oscillator.
circuit design, capacitors C1 and C2 which connect to the earth, are added to the input
and output terminals of the crystal oscillator respectively. The values of the two capacitors
can be flexible, ranging from 6 pF to 22 pF, however, the specific capacitive values depend
on further testing and adjustment on the overall performance of the whole circuit. Normally,
the capacitive values of C1 and C2 are within 10 pF for the 26 MHz crystal oscillator.
Crystal oscillator should be placed as close to the XTAL pins as possible (without the traces
being too long). It is good practice to add high density ground vias around the clock trace
for great insulation.
being too long). It is good practice to add high density ground vias around the clock trace
for great insulation.
There should be no vias on the input and output traces, which means the traces cannot
cross layers.
cross layers.
Place the input and output bypass capacitors on the near left or right side of the chip. Do
not place them on the traces.
not place them on the traces.
Do not route high-frequency digital signal lines in the four-layer board. It is best not to route
any signal line under the crystal oscillator. The larger the copper area on the top layer is, the
better. As crystal oscillator is a sensitive component, do not place magnetic components
such as high current inductance nearby.
any signal line under the crystal oscillator. The larger the copper area on the top layer is, the
better. As crystal oscillator is a sensitive component, do not place magnetic components
such as high current inductance nearby.
Notice:
Please use the most updated download tool and configure SPI MODE in the download tool as DIO or
DOUT
.
Espressif
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6 13
2016.08