ADVANCE
CYW43570
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 CYW43570 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.
Figure 4. Recommended Oscillator Configuration
C*
WRF_XTAL_IN
40.0 MHz
C*
X ohms*
WRF_XTAL_OUT
* Values determined by crystal
drive level. See reference
schematics for details.
A fractional-N synthesizer in the CYW43570 generates the radio frequencies, clocks, and data/packet timing, enabling it to operate
using a wide selection of frequency references.
The recommended default frequency reference is a 40.0 MHz crystal. The signal characteristics for the crystal interface are listed in
Table 4.
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 further details.
Document Number: 002-15054 Rev. *I
Page 13 of 94
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