TDA5235
Functional Description
2.4.4
Crystal Oscillator and Clock Divider
The crystal oscillator is a Pierce type oscillator which operates together with the crystal
in parallel resonance mode. An automatic amplitude regulation circuitry allows the
oscillator to operate with minimum current consumption. In SLEEP Mode, where the
current consumption should be as low as possible, the load capacitor must be small and
the frequency is slightly detuned, therefore all internal trim capacitors are disconnected.
The internal capacitors are controlled by the crystal oscillator calibration registers
XTALCALx. With a binary weighted capacitor array the necessary load capacitor can be
selected.
Whenever a XTALCALx register value is updated, the selected trim capacitors are
automatically connected to the crystal so that the frequency is precise at the desired
value. The SFR control bit XTALHPMS can be used to activate the High Precision Mode
also during SLEEP Mode.
fsys
Setting
automatically
controlled
XTALCAL0
XTALCAL1
9
( ≤ 1pF steps )
(DGND)
XTALHPMS
Oscillator-Core
XTAL1
XTAL2
Figure 7
Crystal Oscillator
Data Sheet
22
V1.0, 2010-02-19
INFINEON [ Infineon ]
