Data Sheet

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Espressif Systems
ESP8266 Datasheet
Table 18 High Frequency Clock
6.2. External Reference Requirements
For an externally generated clock, the frequency can range from 26MHz to 52MHz can be used. For
good performance of the radio, the following characteristics are expected of the clock:
Table 19 External Clock Reference
7. Radio
The ESP8266EX radio consists of the following main blocks:
2.4GHz receiver
2.4GHz transmitter
High speed clock generators and crystal oscillator
Real time clock
Bias and regulators
Power management
Parameter
Symbol
Min
Max
Unit
Frequency
FXO
26
52
MHz
Loading capacitance
CL
32
pF
Motional capacitance
CM
2
5
pF
Series resistance
RS
0
65
Ω
Frequency tolerance
ΔFXO
-15
15
ppm
Frequency vs temperature (-25°C ~
75°C)
ΔFXO,Temp
-15
15
ppm
Parameter
Symbol
Min
Max
Unit
Clock amplitude
VXO
0.2
1
Vpp
External clock accuracy
ΔFXO,EXT
-15
15
ppm
Phase noise @1kHz offset, 40MHz clock
-120
dBc/Hz
Phase noise @10kHz offset, 40MHz clock
-130
dBc/Hz
Phase noise @100kHz offset, 40MHz clock
-138
dBc/Hz
Espressif Systems / August 1, 2015
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