Analog Front End
TDA7521 is a BiCMOS analog front end for CD appli-
cations. Four input signals (AC*, BD*, E* and F*),
coming from the pick-up (whose laser diode is driven
and controlled by the device itself), are preamplified
by a programmable voltage-to-voltage or current-to-
voltage stage, depending on the used pick-up. The
output signals from the preamplifier stage (AC, BD, E,
F and HF, a radio frequency signal obtained by com-
bining 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 con-
trolling revolution speed). All these signals are digi-
tized, multiplexed, synchronized with the external
clock (768×Fs or 394×Fs, Fs=44.1KHz) and fed to the
digital counterpart in one only digital stream (AC/HF/
BD/HF/E/HF/F/HF). Two stereo DACs convert the in-
put bitstreams from TDA7522.
(10 x 10 x 1.40 mm body)
All the clock signals (for ADCs and DACs) are generated by a low-jitter PLL-based clock manager. All
TDA7521’s analog preprocessing is controlled by TDA7522 by means of an UART interface (which imple-
ments an I2C-like protocol). Housed in a TQFP 44, 10×10mm package, TDA7521 features the functions
shown in figure below.
TDA7521 uses the HF4CMOS technology and is supplied @5Vdc.
This is preliminary information on a new product now in development. Details are subject to change without notice.