BCM4330 Preliminary Data Sheet
Frequency References
Section 3: Frequency References
An external crystal is used for generating all radio frequencies and normal operation clocking. As an alternative,
an external frequency reference driven by a temperature-compensated crystal oscillator (TCXO) signal may be
used. In addition, a low-power oscillator (LPO) is provided for lower power mode timing.
Note: The crystal and TCXO implementations have different power supplies (WRF_XTAL_VDD1P2 for
crystal, WRF_TCXO_VDD for TCXO).
Crystal Interface and Clock Generation
The BCM4330 can use an external crystal to provide a frequency reference. The recommended configuration
for the crystal oscillator including all external components is shown in Figure 5. Consult the reference
schematics for the latest configuration.
C
WRF_XTAL_OP
12 – 27 pF
C
X Ohms*
WRF_XTAL_ON
12 – 27 pF
* Resistor value
determined by crystal
drive level. See reference
schematics for details.
Figure 5: Recommended Oscillator Configuration
A fractional-N synthesizer in the BCM4330 generates the radio frequencies, clocks, and data/packet timing,
enabling it to operate using a wide selection of frequency references.
For SDIO applications the default frequency reference is a 37.4 MHz crystal or TCXO. For HSIC applications, the
recommended frequency reference is also 37.4 MHz. The signal characteristics for the crystal interface are
listed in Table 2 on page 34.
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 further details.
®
BROADCOM
BCM4330 Preliminary Data Sheet
April 28, 2011 • 4330-DS304-RI
Page 32
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