LM2467TA datasheet(7/12 Pages) NSC

7 / 12 page

Application Hints (Continued)

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

CC bypass capacitor, located very close to pin 4

and ground pins

•

C20—V

BB bypass capacitors, located close to pin 8 and

ground

•

C46, C47, C48 — V

CC bypass capacitors, near LM2467

and V

CC clamp diodes. Very important for arc protection.

The routing of the LM2467 outputs to the CRT is very critical

to achieving optimum performance.

Figure 13 shows the

routing and component placement from pin 1 of the LM2467

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

that they almost line up from the output pin of the LM2467 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 D8, D9, R24 and D6 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 D8 is connected

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

and direct path to the LM2467 ground pins. The cathode of

D9 is connected to V

CC very close to decoupling capacitor

C19 (see

Figure 13) which is connected to the same section

of the ground plane as D8. The diode placement and routing

is very important for minimizing the voltage stress on the

LM2467 during an arcover event. Lastly, notice that S3 is

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

CRT ground.

LM2467TA Arkusz danych(PDF) 7 Page - National Semiconductor (TI)