BCM4390DKWBGT Datasheet, PDF (18/78 Pages) Cypress Semiconductor – WICED™ Wi-Fi IEEE 802.11 b/g/n SoC with Embedded Application Processor

BCM4390 Advance 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 BCM4390 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
12–27 pF
C
12–27 pF
WRF_XTAL_IN
37.4 MHz
X ohms*
WRF_XTAL_OUT
* Resistor value
determined by crystal
drive level. See reference
schematics for details.
A fractional-N synthesizer in the BCM4390 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 37.4 MHz crystal. The signal characteristics for the crystal
interface are listed in Table 2 on page 18.
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 further details.
BROADCOM ®
February 5, 2014 • 4390-DS103-R
WICED Wi-Fi IEEE 802.11 SoC w/Embedded App Processor
Page 17
BROADCOM CONFIDENTIAL