TDA4800 Datasheet, PDF (6/16 Pages) NXP Semiconductors – Vertical deflection circuit for monitor applications

Philips Semiconductors
Vertical deflection circuit for monitor
applications
Product specification
TDA4800
Flyback generator (pin 9)
The flyback generator has an external capacitor C8 at
pin 9. During scanning, the internal circuit switches pin 9
almost to ground; thereby C8 is charged by the supply
voltage via external components R14 and D2.
During the flyback time pin 9 is switched almost to the
supply voltage, so that the supply voltage for the power
output stage (pin 6) is nearly doubled. This high flyback
voltage ensures a very short flyback time.
Voltage stabilizer
The voltage stabilizer circuit provides a stable operating
voltage of about 7.5 V for several internal circuits of the
TDA4800.
Guard circuit (pin 3)
When the vertical deflection current is absent (e.g.
short-circuited, or open-circuited of the yoke) the guard
circuit changes the blanking pulse at pin 3 into a DC signal
which blanks the beam current to protect the screen.
Also an oscillator defect (C1 short-circuited or
R1 disconnected from pin 1) switches on the guard circuit.
INTERNAL CIRCUITRY
handbook, full pagewidth
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11
12
13
Vstab
TDA4800
1
2
3
4
5
6
Fig.3 Internal circuitry.
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8
9
MHA588
1997 Mar 27
6