BCM43903KUBGT Datasheet, PDF (21/87 Pages) Cypress Semiconductor – WICED™ IEEE 802.11 b/g/n SoC with an Embedded Applications Processor

BCM43903 Preliminary 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 can be used. In addition, a low-power oscillator (LPO) is provided for lower
power mode timing.
Crystal Interface and Clock Generation
The BCM43903 can use an external crystal to provide a frequency reference. The recommended crystal
oscillator configuration, including all external components, is shown in Figure 5. Consult the reference
schematics for the latest configuration.
Figure 5: Recommended Oscillator Configuration
Device boundary
C
27 pF
C
WRF_XTAL_XON
1.3 pF
37.4 MHz
x ohms
WRF_XTAL_XOP
Programmable internal shunt caps are
from 0 pF to 7.5 pF in steps of 0.5 pF.
27 pF _{External resistor and programmable}
internal resistor value is determined
by crystal drive level.
0.4 pF
Programmable internal series resistor is from 50 ohms to 500 ohms
in steps of 50 ohms. Boot-up ROM value is 50 ohms.
Note: A reference schematic is available for further details. Contact your Broadcom FAE.
A fractional-N synthesizer in the BCM43903 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 3 on page 21.
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^®
March 12, 2016 • 43903-DS102-R
BROADCOM CONFIDENTIAL
Page 20