STV0684 Datasheet, PDF (44/49 Pages) STMicroelectronics – Digital Camera Processor

Electrical Characteristics
STV0684
4.7 External circuits
4.7.1
Crystal oscillator
There are 2 crystal oscillator pins XTAL_IN, XTAL_OUT, as shown in Figure 23. The Oscillator cell
architecture is a single stage oscillator with an inverter working as an amplifier. The oscillator stage
is biased by an internal resistor (>1MΩ). It also requires an external PI network consisting of a
crystal and two capacitors.
Note: The TV standards requests that the clock accuracy of the oscillator circuit must be 30ppm or less to
achieve a 500Hz accuracy for 4.5MHz chroma.
Figure 23: Oscillator support circuit
XTALI
XTALO
Crystal
22pF
22pF
4.7.2 Audio
Figure 24: Audio PLL filter and CBS
VC
10K
10nF
680pF
CBS
+
_
10µF
If the record audio section of the STV0684 is not required, AP, CBS, VC and AN can be left
unconnected. Power must still be supplied to VDDA and VDDAP.
4.7.3
Recommended power supply decoupling
A 0.1µF bypass capacitor located as close as possible to the chip package connecting between all VDD pins
and GND and at least one bulk decoupling capacitor on each of the supply rails VDDA, VDDC, VDDI and
VDDP.
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