CDCE906PW datasheet(22/42 Pages) TI

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27 MHz

Crystal

CDCE906

16.9344 MHz (384fs)

33.8688 MHz (768fs)

11.2896 MHz (256fs)

27 MHz

DVD−DSP

MPEG/AC−3

Audio Dec

Karaoke

DSP

PCM1716

Front

Surround

Center

Subwoofer

CPU Clock

64 MHz

i.e. audio rate: 44.1 kHz

Clock Inputs (CLK_IN0 and CLK_IN1)

2LVCMOS

Differential

Input

CLK_IN0

CLK_IN1

Input source select

(from EEPROM)

crystal

unit

ICB

CDCE906

SCAS814H – NOVEMBER 2005 – REVISED DECEMBER 2007

Typical applications for the CDCE906 are digital HDTV systems, gaming consoles, DVD players, DVD add-on

cards for multimedia PCs, and step-top boxes.

Figure 14. CDCE906 System Application Block Diagram

The CDCE906 features two clock inputs which can be used as:

• Crystal oscillator input (default setting)

• Two independent single-ended LVCMOS inputs

• Differential signal input

The dedicated clock input can be selected by the input signal source Bit [7:6] of Byte 11.

Crystal Oscillator Inputs

The input frequency range in crystal mode is 8 MHz to 54 MHz. The CDCE906 uses a Pierce-type oscillator

circuitry with included feedback resistance for the inverting amplifier. The user, however, has to add external

capacitors CX0, CX1) to match the input load capacitor from the crystal (see Figure 15). The required values can

be calculated:

CX0 = CX1 = 2 × CL– CICB,

where CL is the crystal load capacitor as specified for the crystal unit and CICB is the input capacitance of the

device including the board capacitance (stray capacitance of PCB).

For example, for a fundamental 27-MHz crystal with CL of 9 pF and CICB of 4 pF,

CX0 = CX1 = (2 × 9 pF) – 3 pF = 15 pF.

It is important to use a short PCB trace from the device to the crystal unit to keep the stray capacitance of the

oscillator loop to a minimum.

Figure 15. Crystal Input Circuitry

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