September 1989

5

Philips Semiconductors

Preliminary specification

TV and VTR stereo/dual sound processor

TDA8417

PINNING

FUNCTIONAL DESCRIPTION

Anti-aliasing filters

Frequency band limitation is performed by a second order Sallen and Key low-pass filter inserted in the AF signal path

and the identification circuit. This limitation is necessary because of the time-discrete signal processing needed to meet

the Nyquist criterium.

Identification

To enable the identification of the transmitted AF signal (mono, stereo or dual sound), the carrier frequency of the second

channel (E2) is also modulated by an identification signal. The identification signal is a 54.6875 kHz pilot carrier signal

which is 50% amplitude modulated by either a 117.4 Hz signal for stereo transmission or by a 274.1 Hz signal for dual

sound transmission.

The identification section of the circuit consists of a 54 kHz high-pass filter followed by a gain controlled amplifier with an

AM demodulator. The total gain of the high-pass filter and the amplifier is approximately 56 dB. The demodulated

identification signal is filtered by the identification band-pass filters, (117.4 Hz for stereo transmission, 274.1 Hz for dual

sound transmission). The output from either filter is converted to a DC signal by a peak detector and the necessary

hysteresis is performed by a Schmitt-trigger. The resultant DC output signals indicate the status of the transmitter (mono,

stereo or dual sound).

1

Control port C1

2

3

4

Oscillator input (or quartz)

5

Digital ground (0 V)

6

Not connected, but reserved

7

Sound channel input AF2 (E2)

8

Sound channel input AF1 (E1)

9

External AF input (E4)

10

Not connected, but reserved

11

Output A4 AF 2 output

12

Output A3 AF 2 output

13

Output A2 AF 1 output

14

Output A1 AF 1 output

15

16

Analogue ground (0 V)

17

Ripple rejection improvement

18

Mute input

19

Control port C2

20

Not connected, but reserved