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TDA9535L

9.5 NS TRIPLE-CHANNEL HIGH VOLTAGE VIDEO AMPLIFIER WITH VERY LOW STD-BY POWER CONSUMPTION

STMicroelectronics 

TDA9535L

8 VIDEO RESPONSE OPTIMIZATION

The dynamic video response is optimized by care-

fully designing the supply decoupling of the video

board (see Section 8.1), the tracks (see

Section 8.2), then by adjusting the input/output

component network (see Section 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

C11

4.7µF

C10(*)

100nF

VCC

C12(*)

100nF

VDD

C24

4.7µF

TDA9207

TDA9209

R20

15/50Ω

-

IN

+

VREF

TDA9535L/36

GNDS

R10

OUT 150Ω

CRT

L1

R11

0.39µH 150Ω

GND

(*): To be connected as close as possible to the device

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 has to be given to the three out-

put 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.

Reducing this capacitive load is achieved

moving away the output tracks from the other

tracks (especially ground) and by using thin

tracks (<0.5mm), see Figure 13.

– Cross talk: Output and input tracks must be set

apart. We recommend to install input and out-

put tracks on opposite sides of the amplifier.

Once again, this is achievable by using thin

tracks (<0.5 mm) to pass through the pin of the

device, see Figure 13 (b).

– Length: Connection between amplifier output

and cathode must be as short and direct as

possible.

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 Ω)

2. To adjust R20 and R10+R11.

Increasing their value increases the

tR/tF values and decreases 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 and

then to apply the optimization they need.

8/16

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