BCM43455 Preliminary Data Sheet
External Frequency Reference
External Frequency Reference
As an alternative to a crystal, an external precision frequency reference can be used, provided that it meets the
Phase Noise requirements listed in Table 2.
If used, the external clock should be connected to the WRF_XTAL_XOP pin through an external 1000 pF
coupling capacitor, as shown in Figure 6. The internal clock buffer connected to this pin will be turned OFF when
the BCM43455 goes into sleep mode. When the clock buffer turns ON and OFF there will be a small impedance
variation. Power must be supplied to the WRF_XTAL_VDD1P35 pin.
Figure 6: Recommended Circuit to Use With an External Reference Clock
1000 pF
Reference
WRF_XTAL_XOP
Clock
NC
WRF_XTAL_XON
Table 2: Crystal Oscillator and External Clock—Requirements and Performance
External Frequency
Crystala
Referenceb c
Parameter
Conditions/Notes
Min. Typ. Max. Min. Typ. Max. Units
Frequency
2.4G and 5G bands,
IEEE 802.11ac operation
35
–
52
–
52
–
MHz
Frequency
5G Band,
IEEE 802.11n operation only
19
–
52
35
–
52
MHz
d, e
2.4G band IEEE 802.11n
operation, and both bands legacy
IEEE 802.11a/b/g operation only
Between 19 MHz and 52 MHz
Frequency tolerance Without trimming
over the lifetime of
the equipment,
–20
–
20
–20
–
20
–
ppm
pF
including
f
temperature
Crystal load
capacitance
–
–
–
–
16
–
–
–
ESR
–
–
60
–
–
–
–
–
–
–
Ω
Drive level
External crystal must be able to 200
tolerate this drive level.
μW
Input impedance
(WRF_XTAL_XOP)
Resistive
–
–
–
–
–
–
–
30k
–
100k
–
Ω
Capacitive
7.5
–
–
–
7.5
0.2
pF
V
WRF_XTAL_XOP
Input low level
DC-coupled digital signal
0
Broadcom®
November 5, 2015 • 43455-DS109-R
Page 30
BROADCOM CONFIDENTIAL
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