BCM4339 datasheet(13/133 Pages) CYPRESS

13 / 133 page

Document No. 002-14784 Rev. *H

Page 13 of 133

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

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.

WRF_XTAL_OUT

WRF_XTAL_IN

C *

X ohms *

* Values determined by crystal drive

level. See reference schematics for details.

37.4 MHz

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