TDA9535L 查看數據表（PDF） - STMicroelectronics

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TDA9535L

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

STMicroelectronics 

TDA9535L

6 THEORY OF OPERATION

6.1 - General

The TDA9535L is a three-channel video amplifier

supplied by a low supply voltage: VCC (typ.12V)

and a high supply voltage: VDD (up to 115V).

The high values of VDD supplying the amplifier out-

put stage control directly the CRT cathodes (DC

coupling mode).

In DC coupling mode, the application schematic is

very simple and only a few external components

are needed to drive the cathodes. In particular,

Figure 2. Output signal, level adjustments

VDD

(A) Top Non-Lin ear Region

15V

there is no need of the DC-restore circuitry which

is used in classical AC coupling applications.

The output voltage range is wide enough

(Figure 2) to provide simultaneously :

– Cut-off adjustment (B: typ. 25V)

– Video contrast (D: typ. up to 40V),

– Brightness (C:with the remaining voltage

range).

In normal operation, the output video signal must

remain inside the linear region whatever the cut-

off / brightness / contrast adjustment is.

(B) Cut-off Adjust. (25V Typ.)

Blanking pulse

Video Signal

(C) Brightness Adjust. (10V Typ.)

(D) Contrast Adjust. (40V Typ.)

17V

(E) Bottom Non-Linear Region

GND

6.2 - How to choose the high voltage supply value (VDD)

The VDD high supply voltage must be chosen care-

fully. It must be high enough to provide the neces-

sary video adjustment but set to minimum value to

avoid unecessary power dissipation.

Example:

The following example shows how the optimum

VDD voltage value is determined:

– Cut-off adjustment range (B) : 25V

– Max contrast (D) : 40V

Case 1:

10V Brightness (C) adjusted by the preamplifier :

VDD = A + B + C + D + E

VDD = 15V + 25V + 10V + 40V + 17V = 107V

Case 2:

10V Brightness (C) adjusted by the G1 anode:

VDD = A + B + D + E

VDD = 15V + 25V + 40V + 17V = 97V

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