TDA2579B Philips Semiconductors, TDA2579B Datasheet - Page 8

• Manufacturer Part Number: TDA2579B
• Description: Horizontal/vertical synchronization circuit
• Manufacturer: Philips Semiconductors

Philips Semiconductors
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 k between pin 18 and ground.
c. Slow time constant, (with exception of frame blanking period), connect pin 18 via a resistor of 10 k to
d. No switching to slow time constant desired (transmitter identification circuit active), connect a 6.8 V zener diode
Fig.2 illustrates the operation of the 3 phase detector circuits.
September 1990
Horizontal/vertical synchronization circuit
This condition can also be set by using a 3.6 V stabistor diode instead of a resistor.
In this condition the transmitter identification circuit is not active.
between pin 18 and ground.
Fig.2 Timing diagram, phase detectors.
8
Preliminary specification
TDA2579B
12 V, pin 10.