lm2462ta National Semiconductor Corporation, lm2462ta Datasheet - Page 7

• Manufacturer Part Number: lm2462ta
• Description: Monolithic Triple 3 Ns Crt Driver
• Manufacturer: National Semiconductor Corporation

Application Hints
NSC DEMONSTRATION BOARD
Figure 12 shows the routing and component placement on
the NSC LM126X/246X demonstration board. The sche-
matic of the board is shown in Figure 10 and Figure 11 . This
board provides a good example of a layout that can be used
as a guide for future layouts. Note the location of the follow-
ing components:
The routing of the LM2462 outputs to the CRT is very critical
to achieving optimum performance. Figure 13 shows the
routing and component placement from pin 1 of the LM2462
to the blue cathode. The white line through the PCB traces
show the path of the blue video. Note that the components
are placed so that they almost line up from the output pin of
the LM2462 to the blue cathode pin of the CRT connector.
This is done to minimize the length of the video path be-
tween these two components. Note also that D8, D9, R24
and D6 are placed to minimize the size of the video nodes
that they are attached to. This minimizes parasitic capaci-
tance 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 ground plane that has
a short and direct path to the LM2462 ground pins. The
cathode of D9 is connected to V
capacitor C48 (see Figure 13 ) which is connected to the
same section of the ground plane as D8. The diode place-
ment and routing is very important for minimizing the voltage
stress on the LM2462 during an arc-over event. Lastly, no-
tice that S3 is placed very close to the blue cathode and is
tied directly to CRT ground.
• C16, C19 — V
• C17, C20 — V
• C46, C47, C48 — V
pin 4 and ground pins
and ground
and V
CC
clamp diodes. Very important for arc protection.
BB
CC
bypass capacitors, located close to pin 8
bypass capacitor, located very close to
CC
bypass capacitors, near LM2462
(Continued)
CC
very close to decoupling
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