BCM43903 Datasheet, PDF (23/87 Pages) Cypress Semiconductor – WICED™ IEEE 802.11 b/g/n SoC with an Embedded Applications Processor

BCM43903 Preliminary Data Sheet
Frequency Selection
Table 3: Crystal Oscillator and External Clock—Requirements and Performance (Cont.)
Crystal^a
External Frequency
Reference^{b c}
Parameter
Conditions/Notes
Min. Typ. Max. Min. Typ. Max. Units
WRF_XTAL_XON IEEE 802.11n AC-coupled analog –
–
–
1
–
–
V_p-p
input voltage
input
(see Figure 6)
Duty cycle
37.4 MHz clock
–
–
–
40 50 60 %
Phase noise^f
37.4 MHz clock at 10 kHz offset –
–
–
–
–
–129 dBc/Hz
(IEEE 802.11b/g) ^{37.4 MHz clock at 100 kHz offset –}
–
–
–
–
–136 dBc/Hz
Phase noise^f
37.4 MHz clock at 10 kHz offset –
–
–
–
–
–134 dBc/Hz
(IEEE 802.11n,
37.4 MHz clock at 100 kHz offset –
–
–
–
–
–141 dBc/Hz
2.4 GHz)
a. (Crystal) Use WRF_XTAL_XON and WRF_XTAL_XOP.
b. See “External Frequency Reference” on page 21 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 BCM43903 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 • 43903-DS102-R
BROADCOM CONFIDENTIAL
Page 22