Data Sheet

19 | P a g e Espressif Systems Oct 12, 2013
ESP8266 802.11bgn Smart Device
11 Clock Management
11.1 High Frequency Clock
The high frequency clock on ESP8266 is used to drive both the Tx and Rx mixers. This clock is
generated from the internal crystal oscillator and an external crystal. The crystal frequency can
range from 26MHz to 52MHz.
While internal calibration of the crystal oscillator ensures that a wide range of crystals can be
used, in general, the quality of the crystal is still a factor to consider, to obtain reasonable phase
noise. When the crystal selected is sub-optimal due to large frequency drifts or poor Q-factor, the
maximum throughput and sensitivity of the Wi-Fi system is degraded. Please refer to the
application notes on how the frequency offset can be measured.
Parameter
Symbol
Min
Max
Unit
Frequency
F
XO
26
52
MHz
Loading capacitance
C
L
32
pF
Motional capacitance
C
M
2
5
pF
Series resistance
R
S
0
65

Frequency tolerance
F
XO
-15
15
ppm
Frequency vs temperature (-25C ~ 75C)
F
XO,Temp
-15
15
ppm