NSC DEMONSTRATION BOARD

Figure 11 is the schematic for the NSC LM126X_246X 11L

demonstration board that can be used to evaluate the

LM126X and LM2471 combination in a monitor. Figure 12

shows the routing and component placement on the NSC

demonstration board. This board provides a good example

of a layout that can be used as a guide for future layouts.

Note the location of the following components:

•

C19—V

and ground pins

•

C20—V

and ground

•

C46, C47, C48 — V

and V

The routing of the LM2471 outputs to the CRT is very critical

to achieving optimum performance. Figure 13 shows the

routing and component placement from pin 3 of the LM2471

to the red cathode. Note that the components are placed so

that they almost line up from the output pin of the LM2471 to

the red cathode pin of the CRT connector. This is done to

minimize the length of the video path between these two

components. Note also that D1, D2, R23 and D5 are placed

to minimize the size of the video nodes that they are at-

tached to. This minimizes parasitic capacitance in the video

path and also enhances the effectiveness of the protection

diodes. The anode of protection diode D1 is connected

directly to a section of the the ground plane that has a short

and direct path to the LM2471 ground pins. The cathode of

D2 is connected to V

C46 (see Figure 13) which is connected to the same section

of the ground plane as D1. The diode placement and routing

is very important for minimizing the voltage stress on the

LM2471 during an arcover event. Lastly, notice that S1 is

placed very close to the red cathode and is tied directly to

CRT ground.

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