OBSOLETE

LM2436

SNOSA13B – JUNE 2002 – REVISED APRIL 2013

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The LM2436 case temperature must be maintained below 100°C. If the maximum expected ambient temperature

inside the monitor is 70°C and the power dissipation is 4.2W (from Figure 6, 50 MHz max video frequency) then

a maximum heat sink thermal resistance can be calculated:

(1)

This example assumes a capacitive load of 8 pF and no resistive load.

Typical Application

A typical application of the LM2436 is shown in Figure 11. Used in conjunction with an LM1279, a complete video

channel from monitor input to CRT cathode can be achieved. Performance is ideal for 1024 x 768 resolution

displays with pixel clock frequencies up to 100 MHz. Figure 11 is the schematic for the TI demonstration board

that can be used to evaluate the LM1279/2436 combination in a monitor, and Figure 10 shows the response at

the red cathode for this application. The input video rise time is 3.2ns, and the peaking component values are

those recommended in Figure 11. Table 1 shows the typical cathode response of all three channels.

Figure 10. Red Cathode Response

Table 1. LM2436 Cathode Response

Red

7.7 ns / 7%

7.7 ns / 5%

Green

7.7 ns / 6%

7.5 ns / 6%

Blue

7.4 ns / 7%

7.3 ns / 7%

PC Board Layout Considerations

For optimum performance, an adequate ground plane, isolation between channels, good supply bypassing and

minimizing unwanted feedback are necessary. Also, the length of the signal traces from the preamplifier to the

LM2436 and from the LM2436 to the CRT cathode should be as short as possible. The following references are

recommended:

Ott, Henry W., “Noise Reduction Techniques in Electronic Systems”, John Wiley & Sons, New York, 1976.

“Video Amplifier Design for Computer Monitors”, Texas Instruments Application Note 1013.

Pease, Robert A., “Troubleshooting Analog Circuits”, Butterworth-Heinemann, 1991.

Because of its high small signal bandwidth, the part may oscillate in a monitor if feedback occurs around the

video channel through the chassis wiring. To prevent this, leads to the video amplifier input circuit should be

shielded, and input circuit wiring should be spaced as far as possible from output circuit wiring.

8

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