TDA8083

This document specifies a DVB compliant demodulator and forward error correction decoder IC for reception of QPSK or BPSK modulated signals for satellite applications. The Satellite Demodulator and Decoder (SSD) can handle variable symbol rates without adapting the analog filters within the tuner. Typical applications for this device are:
· MCPC (Multi-Channel Per Carrier): one QPSK or BPSK modulated signal in a single satellite channel (transponder)
· Simul-cast: QPSK or BPSK modulated signal together with a Frequency Modulated (FM) signal in a single satellite channel (transponder).

The TDA8083 can handle variable symbol rates in the range of 12 to 30 Msymbols/s with a minimum number of low cost and non-critical external components.

The TDA8083 has minimal interfaces with the tuner. It only requires the demodulated analog I and Q baseband input signals and provides a tuner AGC control signal. Analog-to-digital conversion is done internally by two matched 7-bit ADCs.

The TDA8083 runs on a low frequency crystal which is upconverted to a clock frequency by means of an internal
PLL. Furthermore, the TDA8083 has an internal anti-alias filter, which can cover the range of symbol frequencies without the need to switch external (SAW) filters.

The TDA8083 has a double carrier loop configuration which has excellent capabilities of tracking phase noise.
Synchronization of the FEC unit is done completely internally, thereby minimizing I2C-bus communication.

The output of the TDA8083 allows different output modes (parallel or serial) to interface to a demultiplexer, descrambler or MPEG-2 decoder including a 3-state mode. For evaluation of the TDA8083, demodulator and Viterbi decoder outputs can be made available externally.

The SDD of the TDA8083 can be controlled and monitored by the I²C-bus. A 5-bit bidirectional I/O expander and an interrupt line are available. By sending an interrupt signal, the SDD can inform the microcontroller of its internal status. Separate resets are available for logic only, logic plus the I²C-bus and carrier loops. A switchable I²C-bus loop-through to the tuner is implemented to switch off the I²C-bus connection to the tuner. This reduces phase noise in the tuner in case of I²C-bus crosstalk. Furthermore, for dish control applications hardware supports DiSEqC 1.X and tone burst generation via I²C-bus control. A 22 or a 44 kHz carrier can be generated (tone mode).