PRELIMINARY
CYW4339
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.
3.1 Crystal Interface and Clock Generation
The CYW4339 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 3. Consult the reference schematics for the latest configuration and recom-
mended components.
Figure 3. 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 CYW4339 generates the radio frequencies, clocks, and data/packet timing, enabling the CYW4339
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.
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 Cypress for details.
Document No. 002-14784 Rev. *H
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