TDA2579B View Datasheet(PDF) - Philips Electronics
Part Name
Description
Manufacturer
TDA2579B Datasheet PDF : 21 Pages
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Philips Semiconductors
Horizontal/vertical synchronization circuit
Preliminary specification
TDA2579B
If the new TV station is weak, the sync-noise detector is activated. This will result in a change over of pin 18 voltage from
6.5 V to ≈10 V. When pin 18 exceeds the level of 7.8 V the phase detector is switched to slow time constant and gated
sync pulse condition. The current is also reduced during the vertical blanking period by 1 mA. When desired, most
conditions of the phase detector can also be set by external means in the following way:
a. Fast time constant TV transmitter identification circuit not active, connect pin 18 to earth (pin 9).
b. Fast time constant TV transmitter identification circuit active, connect a resistor of 220 kΩ between pin 18 and ground.
This condition can also be set by using a 3.6 V stabistor diode instead of a resistor.
c. Slow time constant, (with exception of frame blanking period), connect pin 18 via a resistor of 10 kΩ to + 12 V, pin 10.
In this condition the transmitter identification circuit is not active.
d. No switching to slow time constant desired (transmitter identification circuit active), connect a 6.8 V zener diode
between pin 18 and ground.
Fig.2 illustrates the operation of the 3 phase detector circuits.
Fig.2 Timing diagram, phase detectors.
September 1990
8
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