BCM88335 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 may be used. In addition, a low-power oscillator (LPO) is provided for lower
power mode timing.
Crystal Interface and Clock Generation
The BCM88335 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 4. Consult the reference
schematics for the latest configuration and recommended components.
Figure 4: Recommended Oscillator Configuration
C *
WRF_XTAL_IN
37.4 MHz
C *
X ohms *
WRF_XTAL_OUT
* Values determined by crystal drive
level. See reference schematics for details.
A fractional-N synthesizer in the BCM88335 generates the radio frequencies, clocks, and data/packet timing,
enabling the BCM88335 to operate using a wide selection of frequency references.
For SDIO applications, the recommended default frequency reference is a 37.4 MHz crystal. The signal
characteristics for the crystal interface are listed in Table 2 on page 27.
Note: Although the fractional-N synthesizer can support alternative reference frequencies,
frequencies other than the default require support to be added in the driver, plus additional extensive
system testing. Contact Broadcom for details.
Broadcom®
September 23, 2015 • 88335-DS100-R
Page 26
BROADCOM CONFIDENTIAL
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