LM2413 National Semiconductor Corporation, LM2413 Datasheet - Page 6

• Manufacturer Part Number: LM2413
• Description: LM2413 - Monolithic Triple 4 NS CRT Driver, Package: to 220, Pin Nb=11
• Manufacturer: National Semiconductor Corporation

www.national.com
Application Hints
PC Board Layout Considerations
For optimum performance, an adequate ground plane, isola-
tion between channels, good supply bypassing and minimiz-
ing unwanted feedback are necessary. Also, the length of
the signal traces from the preamplifier to the LM2413 and
from the LM2413 to the CRT cathode should be as short as
possible. The red video trace from the LM1283 to the
LM2413 input should be considered as short as possible on
a PCB layout. If possible, position the pre-amp in such a way
where the traces from its output connects to the driver input
the most direct and shortest path. The following references
are recommended for video board designers:
Ott, Henry W., “Noise Reduction Techniques in Electronic
Systems”, John Wiley & Sons, New York, 1976.
“Guide to CRT Video Design”, National Semiconductor Appli-
cation Note 861.
“Video Amplifier Design for Computer Monitors”, National
Semiconductor Application Note 1013.
Pease, Robert A., “Troubleshooting Analog Circuits”,
Butterworth-Heinemann, 1991.
Because of its high small signal bandwidth, the part may os-
cillate in a monitor if feedback occurs around the video chan-
nel through the chassis wiring. To prevent this, leads to the
video amplifier input circuit should be shielded, and input cir-
cuit wiring should be spaced as far as possible from output
circuit wiring.
NSC Demonstration Board
Figure 11 and Figure 12 show routing and component place-
ment on the NSC LM1283/2413 demonstration board. The
schematic of the board is shown in Figure 10 . This board
(Continued)
6
provides a good example of a layout that can be used as a
guide for future layouts. Note the location of the following
components:
The routing of the LM2413 outputs to the CRT is very critical
to achieving optimum performance. Figure 13 shows the
routing and component placement from pin 1 to the blue
cathode. Note that the components are placed so that they
almost line up from the output pin of the LM2413 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 keep
the size of the video nodes to a minimum. This minimizes
parasitic capacitance in the video path and also enhances
the effectiveness of the protection diodes. The anode of pro-
tection diode D14 is connected directly to a section of the
ground plane that has a short and direct path to the LM2413
ground pins. The cathode of D15 is connected to V
close to decoupling capacitor C55 (see Figure 13 ) which is
connected to the same section of the ground plane as D14.
The diode placement and routing is very important for mini-
mizing the voltage stress on the LM2413 during an arc over
event. Lastly, notice that S3 is placed very close to the blue
cathode and is tied directly to CRT ground.
• C79 — V
• C55 — V
• C75 and C77 — V
and ground pins. ( Figure 12 )
ground. ( Figure 12 )
and V
( Figure 11 )
CC
CC
BB
clamp diodes. Very important for arc protection.
bypass capacitor, located close to pin 10 and
bypass capacitor, located very close to pin 6
CC
bypass capacitors, near LM2413
CC
very