LM2438T National Semiconductor, LM2438T Datasheet - Page 7

• Manufacturer Part Number: LM2438T
• Description: IC DRIVER MONOLITHIC TO-220-9
• Manufacturer: National Semiconductor

Specifications of LM2438T

• Display Type: CRT
• Current - Supply: 18mA
• Voltage - Supply: 60 V ~ 85 V
• Operating Temperature: -20°C ~ 100°C
• Mounting Type: Through Hole
• Package / Case: TO-220-9 (Bent and Staggered Leads)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Interface: -
• Configuration: -
• Digits Or Characters: -
• Other names: *LM2438T

Application Hints
NSC DEMONSTRATION BOARD
Figure 12 shows the routing and component placement on
the NSC LM1279/2438 demonstration board. The schematic
of the board is shown in Figure 11 . This board provides a
good example of a layout that can be used as a guide for fu-
ture layouts. Note the location of the following components:
The routing of the LM2438 outputs to the CRT is very critical
to achieving optimum performance. Figure 13 shows the
routing and component placement from pin 1 of the LM2438
• C54, C56 — V
• C43, C44 — V
• C53, C55 — Additional V
pin 4 and ground pins
8 and ground
LM2438 and V
protection.
CC
BB
CC
bypass capacitors, located close to pin
bypass capacitor, located very close to
clamp diodes. Very important for arc
FIGURE 10. Waveform at Cathode with LM1279/243X Demo Board
CC
(Continued)
bypass capacitors, near
7
to the red cathode. Note that the components are placed so
that they almost line up from the output pin of the LM2438 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 D16, D17, R21 and D9 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 D17 is con-
nected directly to a section of the the ground plane that has
a short and direct path to the LM2438 ground pins. The cath-
ode of D16 is connected to V
pacitor C53 (see Figure 13 ) which is connected to the same
section of the ground plane as D17. The diode placement
and routing is very important for minimizing the voltage
stress on the LM2438 during an arcover event. Lastly, notice
that S1 is placed very close to the red cathode and is tied di-
rectly to CRT ground.
DS101043-15
CC
very close to decoupling ca-
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