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TDA3592A

SECAM-PAL transcoder

Philips Electronics 

Philips Semiconductors

SECAM-PAL transcoder

Product specification

TDA3592A

Sandcastle pulse detection

The sandcastle pulse detector requires a three-level sandcastle pulse to provide horizontal blanking, vertical blanking

and burst gate pulses. The detector burst gate pulse triggers a pulse generator which produces two timing pulses, pulse

‘A’ and pulse ‘B’ (see Fig.2). Pulse ‘A’ is used to time the PAL modulator burst and to sample the (R-Y) and (B-Y)

clamping pulse generators. A (R-Y) clamping pulse is generated only during a red line and a (B-Y) clamping pulse only

during a blue line. Pulse ‘B’ times the SECAM horizontal identification.

Fig.2 Burst gate timing pulse generation.

Carrier generation

The carrier signal for the PAL modulator is obtained from a 4,43 MHz oscillator. An internal Miller integrator operates in

conjunction with the decoupling capacitor at pin 10 to provide the required 90° phase shift.

PAL matrix

The signal output from the PAL modulator at pin 9 is sequentially modulated with (R-Y) burst phased in the +(R-Y)

direction, and (B-Y) burst phased in the −(B-Y) direction. This PAL signal is applied directly to pin 11 and via a 64 µs

delay to pin 12. A true PAL signal is constructed in the PAL matrix by means of an additional/substraction process (in a

correct H/2 sequence) using the delayed and undelayed inputs.

January 1988

6

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