TDA8046 查看數據表（PDF） - Philips Electronics

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TDA8046

Multi-mode QAM demodulator

Philips Electronics 

Philips Semiconductors

Multi-mode QAM demodulator

Product specification

TDA8046

7.1.5 CLOCK RECOVERY

The clock recovery function uses the unequalized I and Q

signals, i.e. the half Nyquist filter outputs (see Fig.4).

The clock recovery section generates a control value each

symbol period. As this algorithm is based on the energy

maximization, both main and mid symbols are required at

the input. Consequently, the input data rate is twice the

symbol rate. The schematic diagram of this detector is

illustrated in Fig.11.

The clock generator generates the required internal clocks

from the VCXO clock signal at 4 × rs. The input stage

amplifier of this generator enables the designer to supply

a low amplitude oscillator signal to the TDA8046. The DAC

output current range (ICLK) can be varied via the I2C-bus.

The sign of the output current can also be inverted to

adjust for the correct sign of the VCXO slope.

For characteristics see Chapter 13.

handbook, full pagewidth

external

I

DAC

CLOCK

RECOVERY

ICLK

DETECTOR

rs Iref3

Vref

Q

to

VCXO

4rs

2rs

2

rs

4

from

VCXO

MGG172

Fig.11 Schematic diagram of the clock recovery.

1996 Nov 19

15

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