STV224X datasheet(83/86 Pages) STMICROELECTRONICS

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STV224XH/228XH/223XH - THERMAL CONSIDERATIONS FOR TQFP64 PACKAGE

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10 THERMAL CONSIDERATIONS FOR TQFP64 PACKAGE

Proper cooling of the STV223XH circuit (TQFP64 package) requires particular care.

The value of RthJA given in the datasheet corresponds to the following condition:

The circuit is soldered ABOVE a printed circuit board (with as much ground plane as possible) and it ex-

changes freely with its environment by natural convection and radiation.

This 'ideal' condition may not be possible in a real TV set environment and RthJA may increase above the

given value.

In particular, the worst case is when the circuit is soldered BELOW the chassis board in a confined volume

between the chassis board and the bottom of the TV box. In this case, RthJA may increase.

Recommendations:

■

to perform a quick theoretical temperature evaluation before making the chassis board

■

later on, to perform detailed temperature measurements on the chassis board, in its real environment

Thermal data given in the data sheet allows an estimation of junction and case temperatures to be made.

For estimation on pin temperature, the following additional data, derived from a measurement on a typical

chassis, can be used: RthJP ~ 20°C/W;

Example of temperatures ESTIMATION:

(Reminder: only in the case where the circuit is soldered ABOVE the chassis board in a relatively 'free' en-

vironment).

Dissipated power: Pd = 1.3W.

Ambient temperature : Ta = 60°C (inside the TV set).

Junction temperature: Tj = Ta + RthJA * Pd = 125°C.

Case temperature: Tc = Tj - RthJC * Pd = 112°C.

Pins temperature: Tp = Tj - RthJP * Pd = 99°C.

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