January 1988

4

Philips Semiconductors

Product specification

SECAM-PAL transcoder

TDA3592A

PINNING

FUNCTIONAL DESCRIPTION

Demodulation

The chrominance and identification demodulators of the TDA3592A both share the same reference tuned circuit (pins 23

and 24). The identification circuit automatically detects whether the incoming signal is SECAM or SECAM (NTSC, PAL

or black-and-white).

When the incoming signals are PAL they are diverted via pin 16 to the chrominance output at pin 14 and no signal

demodulation takes place. The delay line connected to pin 16 delays the signals to equalize the delay of the SECAM-PAL

transcoding process. When SECAM signals are received, the PAL signal path is switched off.

Incoming SECAM signals are applied to pin 3 via an external bell filter. The signals are amplified, limited and then

demodulated. Only one demodulator is necessary as the colour difference signals are available sequentially. After

demodulation the colour difference signals are separated by an H/2 switch and then applied to (R-Y) and (B-Y) clamp

circuits where the black levels are clamped to the same DC level. With all conditions at pin 4, artificial black levels are

inserted during the horizontal blanking periods. This is done because of the possibility of horizontal burst signals not

being available. The artificial levels may not be identical to the detected black level due to circuit spread but this can be

corrected by detuning the reference tuned circuit.

1. Ground.

2. Limiter feedback.

3. Limiter input: chrominance input SECAM; identification input SECAM/SECAM.

4. Identification selection input using a DC level to preset the identification mode.

5. Storage capacitor input for floating level identification.

6. Storage capacitor input to SECAM/SECAM identification circuit.

7. Double time-constant input to SECAM/SECAM identification circuit.

8. 4,43 MHz oscillator.

9. Sequentially modulated output.

10. Decoupling capacitor for miller integrator feedback circuit.

11. Direct input chrominance signal.

12. Delayed input chrominance signal.

13. PAL/PAL input signal from PAL decoder.

14. Chrominance output signal.

15. Luminance output signal.

16. Luminance/SECAM input signal.

18. Decoupled positive supply voltage.

19. Three-level sandcastle pulse input.

20. De-emphasis circuit connection: R = 560

Ω; C = 1 nF.

21. Storage capacitor connection for (R

−Y) clamp.

22. Storage capacitor connection for (B

−Y) clamp.

24. As for pin 23.