TDA8417 Philips Semiconductors, TDA8417 Datasheet - Page 5

• Manufacturer Part Number: TDA8417
• Description: TV and VTR stereo/dual sound processor with integrated filters and I2C-bus control
• Manufacturer: Philips Semiconductors

Philips Semiconductors
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).
September 1989
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
TV and VTR stereo/dual sound processor
with integrated filters and I
Control port C1
SDA, serial data line (I
SCL, serial clock line (I
Oscillator input (or quartz)
Digital ground (0 V)
Not connected, but reserved
Sound channel input AF2 (E2)
Sound channel input AF1 (E1)
External AF input (E4)
Not connected, but reserved
Output A4 AF 2 output
Output A3 AF 2 output
Output A2 AF 1 output
Output A1 AF 1 output
Supply voltage V
Analogue ground (0 V)
Ripple rejection improvement
Mute input
Control port C2
Not connected, but reserved
P
2
2
C-bus)
C-bus)
2
C-bus control
5
Preliminary specification
TDA8417