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Flashover protection, Switch-off behaviour, Video output amplifier tda6106q – Philips TDA6106Q User Manual

Page 7

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1997 Mar 03

7

Philips Semiconductors

Product specification

Video output amplifier

TDA6106Q

Fig.4 Output voltage (pin 8 falling edge) as a function of AC input signal.

150
140

100

60
50

51

49

s

t

overshoot (in %)

t

t

0

x

x

t f

pd

t

Voc

Vi

MGA975

Flashover protection

The TDA6106Q incorporates a protection diode against
CRT flashover discharges that clamp the cathode output
voltage to a maximum of V

DD

+ V

diode

. To limit the diode

current, an external 1.5 k

carbon high-voltage resistor in

series with the cathode output and a 2 kV spark gap are
needed (for this resistor-value, the CRT has to be
connected to the main PCB). This addition produces an
increase in the rise and fall times of approximately 7.5 ns
and a decrease in the overshoot of approximately 1.3%.

V

DD

to GND must be decoupled:

1. With a capacitor larger than 20 nF with good HF

behaviour (e.g. foil). This capacitor must be placed as
close as possible to pins 6 and 4, but definitely within
5 mm.

2. With a capacitor larger than10

µ

F on the picture tube

base print (shared by three output stages).

Switch-off behaviour

The output pins of the TDA6106Q are still under the control
of the input pin for a supply voltage down to approximately
30 V.