Infineon Cypress WICED BCM43903, Руководство пользователя

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Document Number: 002-14826 Rev. *G Page 14 of 65
PRELIMINARY
CYW43903
3.2 External Frequency Reference
As an alternative to a crystal, an external precision frequency reference can be used, provided that it meets the phase noise require-
ments listed in
Table 4 .
If used, the external clock should be connected to the WRF_XTAL_XON pin through an external 1000 pF coupling capacitor, as shown
in
Figure 6 . The internal clock buffer connected to this pin will be turned off when the CYW43903 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_VDD1P35 pin.
Figure 6. Recommended Circuit to Use With an External Reference Clock
Table 4. Crystal Oscillator and External Clock—Requirements and Performance
Parameter Conditions/Notes
Crystal
1
1. (Crystal) Use WRF_XTAL_XON and WRF_XTAL_XOP.
External Frequency
Reference
2
2. See External Frequency Reference for alternative connection methods.
Units Min. Typ. Max. Min. Typ. Max.
Frequency 2.4 GHz and 5 GHz bands:
IEEE 802.11a/b/g/n operation – 37.4 – – –37.4 – MHz
Frequency tolerance over the
lifetime of the equipment,
including temperature
3
3. It is the responsibility of the equipment designer to select oscillator components that comply with these specifications.
Without trimming –20 – 20 –20 – 20 ppm
Crystal load capacitance – – 16 – – – – pF
ESR – – – 60 – – – Ω
Drive level External crystal must be able to
tolerate this drive level.
200 – – – – – µW
Input impedance
(WRF_XTAL_XON)
Resistive – – – 30k 100k – Ω
Capacitive – – 7.5 – – 7.5 pF
WRF_XTAL_XON
Input low level
DC-coupled digital signal – – – 0 – 0.2 V
WRF_XTAL_XON
Input high level
DC-coupled digital signal – – – 1.0 – 1.26 V
WRF_XTAL_XON
input voltage
(see Figure 6 )
IEEE 802.11b/g operation only – – – 400 – 1200 mV
p-p
WRF_XTAL_XON
input voltage
(see Figure 6 )
IEEE 802.11n AC-coupled analog
input
– – – 1 – – V
p-p
Duty cycle 37.4 MHz clock – – – 40 50 60 %
Phase noise
4
(IEEE 802.11b/g)
4. Assumes that external clock has a flat phase noise response above 100 kHz.
37.4 MHz clock at 10 kHz offset – – – – – –129 dBc/Hz
37.4 MHz clock at 100 kHz offset – – – – – –136 dBc/Hz
Phase noise
4
(IEEE 802.11n, 2.4 GHz)
37.4 MHz clock at 10 kHz offset – – – – – –134 dBc/Hz
37.4 MHz clock at 100 kHz offset – – – – – –141 dBc/Hz
Reference
Clock
NC
1000 pF
WRF_XTAL_XON
WRF_XTAL_XOP