THOMSON 2200
Service Manual

4 AUDIO OUTPUT
The STi5508 supports both a six channel analog output and a stereo output configuration. Both of these output configurations are available simultaneously (eight analog outputs total). In a system configuration with six analog outputs, the front left and right channels can be configured to provide the stereo outputs, Dolby Surround, and SRS TruSurround, or the left and right front channels for a 5.1 channel surround system. The STi5508 also provides a stereo output channel that can be used in combination with the 5.1 outputs. An example of this configuration is a DVD player with these stereo outputs connected to the TV and the six channel outputs connected to the surround sound amplifier unit. In this setup, the consumer can use the TV speakers or the surround speaker without changing any wires. The stereo output can be configured separately from the six-channel left and right outputs, so, for example, the stereo output can be configured for Dolby ProLogic. The Sti5508 also provides digital output in S/PDIF format. The evaluation board supports both optical and coaxial S/PDIF outputs.

4.1

AUDIO DACS
2

The STi5508 supports several variations of an I S type bus, varying the order of the data bits (leading or no leading zero bit, left or right alignment within frame, and MSB or LSB first) is possible using the 2 Sti5508 internal configuration registers. The I S format uses four stereo data lines and three clock lines. 2 The I S data and clock lines can be connected directly to one or more audio DAC to generate analog audio output. The evaluation board uses a six-channel DAC and also a two-channel DAC. The six-channel DAC is connected to the three STI5508 data signals for six-channel output and the two-channel DAC is connected to the STi5508 optional stereo output. The board can be configured with either the six- or twochannel DAC, or both. When the two-channel DAC is not used, the left and right front audio can be connected to the stereo audio output connectors by installing zero ohm resistors R364 and R365. The six-channel DAC is an AKM AK4356. The two-channel DAC is an AK4394 also made by AKM. Both of these DACs support up to 192Khz sampling rate. A less expensive 96kHz two-channel DAC with the same pin-out can be placed instead of the AK4394. Four STi5508 PIO pins are used to configure the audio DACs. The outputs of the DACs are differential, not single ended so a slightly more expensive buffering circuit is required. The buffer circuits use NJR NJM5532 opamps to perform the low-pass filtering and the buffering.

4.2

AUDIO MUTE

The audio DACs contain an internal mute circuit and can be enabled by the STi5508 PIO pins. The evaluation board may output a small �pop� when the system is powered on and off, but no audible pops should be heard during operation or when entering or leaving standby mode.

5 VIDEO INTERFACE
The STi5508 integrates a PAL/NTSC encoder. It converts the digital MPEG/Sub Picture/OSD stream into a standard analog baseband PAL/NTSC signals. Six analog video outputs provide CVBS, SVideo (Y/C), and RGB/YUV formats. The three RGB signals can be configured via an internal STi5508 register setting to output either RGB or YUV video signals.