2.4.3 System Clock
126.96.36.199 Crystal Oscillator
The reference clock for the Digital and the RF Section is generated by a pierce-type
crystal oscillator. Adjustable internal load capacitors are provided that allow the
tolerances of the crystal, external load capacitors and the IC itself to be trimmed out.
These capacitors are built of binary weighted C-banks and are connected in parallel to
the external load capacitors. The internal capacitors are controlled by the crystal
oscillator calibration data register (XTALCAL). An automatic amplitude regulation allows
the oscillator to operate with minimal current consumption.
All trim capacitors are disconnected in Sleep Mode (this minimizes current
consumption). Whenever the TDA523x switches from Sleep Mode to Run Modes, the
Master Control Unit reads out the XTALCAL0 and XTALCAL1 registers and connects the
selected trim capacitors to the crystal. A modification of XTALCAL0 or XTALCAL1
registers in Run Modes does not immediately alter the setting of the activated trim
capacitors unless the SFR control bit XTALTREN, is set.
Figure 14 Crystal Oscillator
The recommended crystal type and manufacturer is listed in the Bill of Materials in the
Evaluation Board section of this Data Sheet. This crystal has been released by Infineon
as well by the crystal manufacturer for optimal operation with TDA523x.
If additional crystal types are released, this information will be published on the related
TDA523x product page at www.infineon.com.
Version 4.0, 2007-06-01