BCM43907 Preliminary Data Sheet
Frequency Selection
Table 3: Crystal Oscillator and External Clock—Requirements and Performance (Cont.)
External Frequency
Crystala
Referenceb c
Parameter
Conditions/Notes
Min. Typ. Max. Min. Typ. Max. Units
WRF_XTAL_XON IEEE 802.11a/b/g operation only –
input voltage
(see Figure 6)
–
–
–
–
400
–
–
1200 mV
p-p
WRF_XTAL_XON IEEE 802.11nAC-coupled analog –
1
–
V
p-p
input voltage
(see Figure 6)
input
Duty cycle
37.4 MHz clock
–
–
–
–
–
–
–
–
40
–
50
–
60
%
f
37.4 MHz clock at 10 kHz offset
–129 dBc/Hz
–136 dBc/Hz
Phase noise
37.4 MHz clock at 100 kHz offset –
37.4 MHz clock at 10 kHz offset
37.4 MHz clock at 100 kHz offset –
37.4 MHz clock at 10 kHz offset
37.4 MHz clock at 100 kHz offset –
–
–
(IEEE 802.11b/g)
f
–
–
–
–
–
–
–
–
–
–137 dBc/Hz
–144 dBc/Hz
Phase noise
(IEEE 802.11a)
f
–
–
–
–
–
–
–
–
–
–134 dBc/Hz
–141 dBc/Hz
Phase noise
(IEEE 802.11n,
2.4 GHz)
f
37.4 MHz clock at 10 kHz offset
–
–
–
–
–
–
–
–
–
–142 dBc/Hz
–149 dBc/Hz
Phase noise
37.4 MHz clock at 100 kHz offset –
(IEEE 802.11n,
5 GHz)
a. (Crystal) Use WRF_XTAL_XON and WRF_XTAL_XOP.
b. See “External Frequency Reference” on page 25 for alternative connection methods.
c. For a clock reference other than 37.4 MHz, 20 × log10(f/ 37.4) dB should be added to the limits, where f = the
reference clock frequency in MHz.
d. The frequency step size is approximately 80 Hz.
e. It is the responsibility of the equipment designer to select oscillator components that comply with these
specifications.
f. Assumes that external clock has a flat phase noise response above 100 kHz.
Frequency Selection
Any frequency within the ranges specified for the crystal and TCXO reference may be used. These include not
only the standard handset reference frequencies of 19.2, 19.8, 24, 26, 33.6, 37.4, 38.4, and 52 MHz, but also
other frequencies in this range, with approximately 80 Hz resolution. The BCM43907 must have the reference
frequency set correctly in order for any of the external interfaces to function correctly, since all bit timing is
derived from the reference frequency.
Note: The fractional-N synthesizer can support many reference frequencies. However, frequencies
other than the default require support to be added in the driver plus additional, extensive system
testing. Contact Broadcom for more information.
Broadcom®
March 12, 2016 • 43907-DS104-R
Page 26
BROADCOM CONFIDENTIAL
CYPRESS [ CYPRESS ]
