BCM43903KUBGT Datasheet, PDF (22/87 Pages) Cypress Semiconductor – WICED™ IEEE 802.11 b/g/n SoC with an Embedded Applications Processor

BCM43903 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 3.
If used, the external clock should be connected to the WRF_XTAL_XON 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 BCM43903 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
Reference
Clock
1000 pF
NC
WRF_XTAL_XON
WRF_XTAL_XOP
Table 3: Crystal Oscillator and External Clock—Requirements and Performance
Crystal^a
External Frequency
Reference^{b c}
Parameter
Conditions/Notes
Min. Typ. Max. Min. Typ. Max. Units
Frequency
2.4 GHz band:
IEEE 802.11n operation and
Between 19 MHz and 52 MHz ^d
legacy IEEE 802.11b/g operation
Frequency tolerance Without trimming
over the lifetime of
the equipment,
including
temperature^e
–20 –
20 –20 –
Crystal load
–
capacitance
–
16 –
–
–
ESR
–
–
–
60 –
–
Drive level
External crystal must be able to 200 –
–
–
–
tolerate this drive level.
Input impedance Resistive
(WRF_XTAL_XON) _Capacitive
–
–
–
30k 100k
–
–
7.5 –
–
WRF_XTAL_XON DC-coupled digital signal
Input low level
–
–
–
0
–
WRF_XTAL_XON DC-coupled digital signal
Input high level
–
–
–
1.0 –
WRF_XTAL_XON IEEE 802.11b/g operation only –
–
–
400 –
input voltage
(see Figure 6)
20
–
–
–
–
7.5
0.2
1.26
1200
ppm
pF
Ω
µW
Ω
pF
V
V
mV_p-p
Broadcom^®
March 12, 2016 • 43903-DS102-R
BROADCOM CONFIDENTIAL
Page 21