
TDA9533
10/16
8 - VIDEO RESPONSE OPTIMIZATION
The dynamic video response is optimized by care-
fully designing the supply decoupling of the video
board (see 8.1), the tracks (see 8.2), then by ad-
justing the input/output component network (see
8.3).
For dynamic measurements such as rise/fall time
and bandwidth, a 8pF load is used (total load in-
cluding the parasitic capacitance of the PC board
and CRT Socket).
Figure 5. Video response optimization for one channel
8.1 - Supply decoupling
The decoupling of VCC and VDD through good
quality HF capacitors (respectively C10 and C12)
close to the device is necessary to improve the dy-
namic performance of the video signal.
8.2 - Tracks
Careful attention must be given to the three output
channels of the amplifier.
– Capacitor: The parasitic capacitive load on the
amplifier outputs must be as small as possible.
Figure 11 clearly shows the deterioration of the
tR/tF when the capacitive load increases. Reduc-
ing this capacitive load is achieved moving away
the output tracks from the other tracks (especial-
ly ground) and by using thin tracks (<0.5mm),
see Figure 12.
– Cross talk: Output and input tracks must be set
apart.
– Length: Connection between amplifier output
and cathode must be as short and direct as pos-
sible.
8.3 - Network adjustment
Video response is always a compromise between
several parameters. An improvement of the rise/
fall time leads to a deterioration of the overshoot.
The recommended way to optimize the video re-
sponse is:
1
To set R10+R11 for arcing protection
(min. 300
)
2
To adjust R20 and R10+R11.
Increasing their value increases the
tR/tF values and decrease the overshoot
3
To adjust L1
Increasing L1 speeds up the device and
increases the overshoot.
We recommend our customers to use the sche-
matic shown on Figure 5 as a starting point for the
video board design and then to apply the optimiza-
tion they need.
C24
4.7
F
C11
4.7
F
R10
L1
R11
CRT
R20
15/50
OUT
VCC
VDD
TDA9207
TDA9209
TDA9533/30
GND
IN
Vref
150
150
0.39
H
(*): To be connected as close as possible to the device
C10(*)
100nF
C12(*)
100nF
GNDS
Cut-off