STMicroelectronics TDA7521
TDA7521 is a BiCMOS analog front end for CD applications. The output signals from the preamplifier stage (AC, BD, E, F and HF, a radio frequency signal obtained by combining the photo-detector outputs as A+B+C+D) are fed to an 8-bit HF ADC (for HF, which carries encoded audio data) and a 6-bit Servo ADC (for AC, BD, E and F, used for focusing, tracking the laser beam and controlling revolution speed).| Part No. | TDA7521 |
|---|---|
| Datasheet | TDA7521 Download |
| Manufacturer |  STMicroelectronics |
| Description | Analog Front End |
| Buy | Stock & Price |
DESCRIPTION
1.1 Clock source and generation The master clock to operate the device is 768 ×Fs (High Frequency mode, HFM) or 384 ×Fs (Low Frequency mode, LFM). Fs=44.1KHz for CD applications. In either case, the clock is generated by TDA7522: an internal low-jitter Charge-Pump PLL (CPPLL) and a Finite State Machine (FSM) synthesize all the needed clocks for the internal blocks: a 512 ×Fs for the DAC and three 384 ×Fs (HFM) or 192×Fs (LFM), with different phases for ADCs and output digital multiplexer. The required loop filter network is made up of a 160pF capacitor from FILT to GND_pll in parallel with the series of a 10nF and a 4K Ω resistor. All clockrelated setups are communicated to TDA7521 via UART interface. 1.2 Voltage references REFIN is an internal voltage reference generated by a resistor divider between VCC_dac and VSS_dac. Nominal value (with VCC_dac=5V) is REFIN=2.5V. Careful filtering of this pin is essential; recommended value of external capacitor is 47 µF paralleled with 100nF ceramic.
