PRELIMINARY
CYW43340
Table 3. Crystal Oscillator and External Clock – Requirements and Performance (Cont.)
Crystala
External Frequency
Referenceb,c
Typ
Parameter
Conditions/Notes
Min
–20
Typ
Max
20
Min
–20
Max
20
Units
ppm
Frequency tolerance over Without trimming
the lifetime of the
–
–
equipment, including
temperature
Duty cycle
37.4 MHz clock
–
–
–
–
–
–
–
–
–
40
–
50
–
60
%
Phase Noise
(802.11b/g)
37.4 MHz clock at 10 kHz offset
–131
–138
dBc/Hz
dBc/Hz
37.4 MHz clock at 100 kHz or greater
offset
–
–
Phase Noise
(802.11a)
37.4 MHz clock at 10 kHz offset
–
–
–
–
–
–
–
–
–
–
–139
–146
dBc/Hz
dBc/Hz
37.4 MHz clock at 100 kHz or greater
offset
Phase Noise
(802.11n, 2.4 GHz)
37.4 MHz clock at 10 kHz offset
–
–
–
–
–
–
–
–
–
–
–136
–143
dBc/Hz
dBc/Hz
37.4 MHz clock at 100 kHz or greater
offset
Phase Noise
(802.11n, 5 GHz)
37.4 MHz clock at 10 kHz offset
–
–
–
–
–
–
–
–
–
–
–144
–151
dBc/Hz
dBc/Hz
37.4 MHz clock at 100 kHz or greater
offset
a. (Crystal) Use WRF_XTAL_OP and WRF_XTAL_ON, internal power to pin WRF_XTAL_VDD1P2.
b. (TCXO) See “TCXO” on page 11 for alternative connection methods.
c. For a clock reference other than 37.4 MHz, 20 × log10(f/ 37.4) dB should be added to the limits, where f = the reference clock frequency in MHz.
d. BT_TM6 should be tied low for a 52 MHz clock reference. For other frequencies, BT_TM6 should be tied high. Note that 52 MHz is not an auto-detected
frequency using the LPO clock.
e. The frequency step size is approximately 80 Hz resolution.
f. The crystal should be capable of handling a 200uW drive level from the CYW43340.
3.3 Frequency Selection
Any frequency within the ranges specified for the crystal and TCXO reference may be used. These include not only the standard
handset reference frequencies of 19.2, 19.44, 19.68, 19.8, 20, 26, 37.4, and 52 MHz, but also other frequencies in this range, with
approximately 80 Hz resolution. The CYW43340 must have the reference frequency set correctly in order for any of the UART or PCM
interfaces to function correctly, since all bit timing is derived from the reference frequency.
Note: The fractional-N synthesizer can support many reference frequencies. However, frequencies other than the default
require support to be added in the driver plus additional, extensive system testing. Contact Cypress for further details.
The reference frequency for the CYW43340 may be set in the following ways:
■ Set the xtalfreq=xxxxx parameter in the nvram.txt file (used to load the driver) to correctly match the crystal frequency.
■ Auto-detect any of the standard handset reference frequencies using an external LPO clock.
For applications such as handsets and portable smart communication devices, where the reference frequency is one of the standard
frequencies commonly used, the CYW43340 automatically detects the reference frequency and programs itself to the correct
reference frequency. In order for auto frequency detection to work correctly, the CYW43340 must have a valid and stable 32.768 kHz
LPO clock that meets the requirements listed in Table 4 on page 14 and is present during power-on reset.
Document Number: 002-14943 Rev. *L
Page 13 of 96
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