STV8217T datasheet(20/149 Pages) STMICROELECTRONICS

20 / 149 page

System Clock

STV82x7

20/149

System Clock

The System Clock integrates 2 independent frequency synthesizers.

The first frequency synthesizer can be used in one of two modes:

● In Mode 1, it is used by the demodulator, and the frequecy is 49.152 MHz.

● In Mode 2, it is used by the I²S input and is synchronous with the input frequency (fS = 32, 44.1

or 48 kHz) and the frequency is 49.152 MHz (for fS = 32 or 48 KHz) or 45.1584 MHz (for fS =

44.1 KHz).

The second frequency synthesizer is used by the DSP core and can be adjusted between 100 and

150 MHz depending on the application (around 106 MHz at reset value).

The default values are designed for a standard 27-MHz reference frequency provided by a stable

single crystal or an external differential clock signal (for example, from the STV35x0) depending on

the CLK_SEL pin configuration (CLK_SEL = 1 means a single crystal, 0 means an external

differential clock). The 27-MHz value is the recommended frequency for minimizing potential RF

interference in the application. The sinusoidal clock frequency, and any harmonic products, remain

outside the TV picture and sound IFs (PIF/SIF) and Band-I RF.

Note:

A change in the reference frequency is compatible with other default I²C programming values,

including those of the built-in Automatic Standard Recognition System.

STV8217T Fiches technique(PDF) 20 Page - STMicroelectronics