BCM4339XKWBGT Datasheet, PDF (32/183 Pages) Cypress Semiconductor – Single-Chip 5G WiFi IEEE 802.11ac MAC/Baseband/Radio with Integrated Bluetooth 4.1 and FM Receiver

BCM4339 Preliminary Data Sheet
External Frequency Reference
External Frequency Reference
As an alternative to a crystal, an external precision frequency reference can be used. The recommended default
frequency is 37.4 MHz. This must meet the phase noise requirements listed in Table 2.
If used, the external clock should be connected to the WRF_XTAL_IN pin through an external 1000 pF coupling
capacitor, as shown in Figure 5. The internal clock buffer connected to this pin will be turned off when the
BCM4339 goes into sleep mode. When the clock buffer turns on and off, there will be a small impedance
variation. Power must be supplied to the WRF_XTAL_BUCK_VDD1P5 pin.
Figure 5: Recommended Circuit to Use with an External Reference Clock
Reference
Clock
1000 pF
NC
WRF_XTAL_IN
WRF_XTAL_OUT
Table 2: Crystal Oscillator and External Clock—Requirements and Performance
Crystal^a
External Frequency
Reference^{b c}
Parameter
Conditions/Notes
Min. Typ. Max. Min. Typ. Max. Units
Frequency
2.4 GHz and 5 GHz bands,
IEEE 802.11ac operation
35 37.4 38.4 –
37.4 –
MHz
Frequency
5 GHz band, IEEE 802.11n
operation only
19 37.4 38.4 35 37.4 38.4 MHz
Frequency
2.4 GHz band IEEE 802.11n
operation, and both bands
legacy 802.11a/b/g operation
only
Ranges between 19 MHz and 38.4 MHz^d
Frequency tolerance Without trimming
over the lifetime of the
equipment, including
temperature^e
–20 –
20 –20 –
20 ppm
Crystal load
–
capacitance
–
12 –
–
–
–
pF
ESR
–
–
–
60 –
–
–
Ω
Drive level
External crystal must be able to 200 –
–
–
–
–
µW
tolerate this drive level.
Input impedance
(WRF_XTAL_IN)
Resistive
Capacitive
–
–
–
30k 100k –
Ω
–
–
7.5 –
–
7.5 pF
WRF_XTAL_IN
input low level
DC-coupled digital signal
–
–
–
0
–
0.2 V
Broadcom^®
November 17, 2014 • 4339-DS106-R
Page 31