BCM4330 Preliminary Data Sheet
Frequency Selection
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 12, 13, 14.4, 16.2, 16.8, 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 BCM4330
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 Broadcom for further details.
The reference frequency for the BCM4330 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 BCM4330 automatically detects the reference
frequency and programs itself to the correct reference frequency. In order for auto frequency detection to
work correctly, the BCM4330 must have a valid and stable 32.768 kHz LPO clock that meets the requirements
listed in Table 3 on page 37 and is present during power-on reset.
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BROADCOM
BCM4330 Preliminary Data Sheet
April 28, 2011 • 4330-DS304-RI
Page 36
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