TDA8153 datasheet(10/11 Pages) STMICROELECTRONICS

10 / 11 page

Power Dissipation

Taking as reference the IC internal schematic dia-

gram we can calculate the power dissipated by the

video amplifiers.

The power dissipation of the IC is defined by a static

an a dynamic part.

The statically dissipated power is given by :

= 3Vht







Vht

− Vobl

Vobl







− 3

Vobl

− 3

(Vref + 2Vbe)2

Where Rf is the feedback resistance and Rb the

input to ground resistance with a black level

Vobl = 150V, Vht = 200V, Rf = 68k

Ω and Rb = 1.8kΩ

we have : PS = 1.75W

The dynamic power dissipation has been calcu-

lated with a 5MHz, 80Vpp sinusoidal output signal

and a load capacitor CL = 10pF with the following

expression :







0.8 Vht

(2f CL Vop

) − 0.8

Vop

2Rf







= 1.90W

The value is reduced by 20% (0.8 factor) because

during the flyback time there is not signal.

The total power dissipated by the IC is therefore :

PT =PS +Pd = 1.75 + 1.90 = 3.65W

One of the worst working condition of the TV set as

regards the power dissipation, is when you get

white noise on the screen, for example, when you

disconnect the TV aerial or the channels are not

properly tuned.

In these cases if we set the TV receiver for 80VPP

white noise output signal with a black level

Vob1 = 125V, the total power dissipated by the IC

can be measured.

It results about PT = 4.8W.

With a maximum ambient temperature of 70

°Cand

a junction temperature of 150

°Ca 15°C/W heatsink

is required.

Figure 4 : Maximum Allowable Power Dissipation

versus Ambient Temperature

Figure 5 : Mounting Examples

TDA8153

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