CYW4343X
3. Frequency References
An external crystal is used for generating all radio frequencies and normal operation clocking. As an alternative, an external fre-
quency reference driven by a temperature-compensated crystal oscillator (TCXO) signal may be used. No software settings are
required to differentiate between the two. In addition, a low-power oscillator (LPO) is provided for lower power mode timing.
3.1 Crystal Interface and Clock Generation
The CYW4343X can use an external crystal to provide a frequency reference. The recommended configuration for the crystal oscil-
lator, including all external components, is shown in Figure 15. Consult the reference schematics for the latest configuration.
Figure 15. Recommended Oscillator Configuration
C
WLRF_XTAL_XOP
12 – 27 pF
C
WLRF_XTAL_XON
R
12 – 27 pF
Note: Resistor value determined by crystal drive level.
See reference schematics for details.
The CYW4343X uses a fractional-N synthesizer to generate the radio frequencies, clocks, and data/packet timing so that it can
operate using numerous frequency references. The frequency reference can be an external source such as a TCXO or a crystal
interfaced directly to the CYW4343X.
The default frequency reference setting is a 37.4 MHz crystal or TCXO. The signal requirements and characteristics for the crystal
interface are shown in Table 3 on page 23.
Note: Although the fractional-N synthesizer can support many reference frequencies, frequencies other than the default require
support to be added in the driver, plus additional extensive system testing. Contact Broadcom for further details.
3.2 TCXO
As an alternative to a crystal, an external precision TCXO can be used as the frequency reference, provided that it meets the phase
noise requirements listed in Table 3 on page 23.
If the TCXO is dedicated to driving the CYW4343X, it should be connected to the WLRF_XTAL_XOP pin through an external capac-
itor with value ranges from 200 pF to 1000 pF as shown in Figure 16.
Document No. 002-14797 Rev. *H
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