good example of a layout that can be used as a guide for fu-

ture layouts. Note the location of the following components:

•

C55 — V

and ground pins

•

C43, C44 — V

8 and ground

•

C53–C56 — V

V

The routing of the LM2437 outputs to the CRT is very critical

to achieving optimum performance.

Figure 12 shows the

routing and component placement from pin 1 of the LM2437

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

that they almost line up from the output pin of the LM2437 to

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

minimize the length of the video path between these two

components. Note also that D14, D15, R29 and D13 are

placed to minimize the size of the video nodes that they are

attached to. This minimizes parasitic capacitance in the

video path and also enhances the effectiveness of the pro-

tection diodes. The anode of protection diode D14 is con-

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

a short and direct path to the LM2437 ground pins. The cath-

ode of D15 is connected to V

pacitor C55 (see

Figure 12) which is connected to the same

section of the ground plane as D14. The diode placement

and routing is very important for minimizing the voltage

stress on the LM2437 during an arcover event. Lastly, notice

that S3 is placed very close to the blue cathode and is tied

directly to CRT ground.

www.national.com

6