LM2402 NSC | Alldatasheet
Document overview
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Technical content
Features
n Rise/fall times typically 3.0/2.8 ns with 8 pF load at
40 VPP
n Well matched with LM2202 video preamps n Output swing capability: 50 VPP for VCC = 80V n 1V to 5V input range n Stable with 0-20 pF capacitive loads and inductive peaking networks n Convenient TO-220 staggered lead package style n Standard LM240X family pinout which is designed for easy PCB layout
Applications
n CRT driver for color monitors with display resolutions up to 1600 x 1200 n Pixel clock frequency up to 200 MHz Schematic and Connection Diagrams DS101016-1 FIGURE 1. Simplified Schematic Diagram
for the evaluation of the LM2402. rise and fall times show about the same overall variation. little increase in the rise time. circuit shown inFigure 2as a function of case temperature. to be operated over a case temperature of 100˚C. Figure 6shows the total power dissipation of the LM2402 vs.
- The designer should also remember that the actual video
3.8W, including both the 80V and 12V supplies.
100 MHz square wave during active video (a pixel clock of
channel from monitor input to CRT cathode can be achieved. and pixel clock frequencies at 200 MHz. used to evaluate the LM2202/2402 combination in a monitor. Systems”, John Wiley & Sons, New York, 1976. Semiconductor Application Note 1013. Butterworth-Heinemann, 1991. Figure 10. This board provides a
- C47 -V CC bypass capacitor, located very close to pin 6 and ground pins. (Figure 12)
- C49 -V BB bypass capacitor, located close to pin 10 and ground. (Figure 12)
- C46 and C77-V CC bypass capacitors, near LM2402 and VCC clamp diodes. Very important for arc protection. (Fig- ure 11) The routing of the LM2402 outputs to the CRT is very critical to achieving optimum performance.Figure 13shows 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 LM2402 to the blue www.national.com5
Application Hints(Continued) cathode pin of the CRT connector. This is done to minimize the length of the video path between these two components. The direct video path is shown in by a dark gray line through the components and the PCB traces. Note also that D24, D25, R58 and D19 are placed to keep the size of the video nodes to a minimum (R58 is located under D19). This mini- mizes parasitic capacitance in the video path and also en- hances the effectiveness of the protection diodes. The traces in the video nodes to these components are shown by the white line. The anode of protection diode D25 is connected directly to the ground plane giving a short and direct path to the LM2402 ground pins. The cathode of D24 is connected to V CC very close to decoupling capacitor C78 (Figure 13) which is connected to the same section of the ground plane as D25. The diode placement and routing is very important for minimizing the voltage stress on the LM2402 during an arc-over event. Lastly, notice that S3 is placed very close to the blue cathode and is tied directly to CRT ground. www.national.com 6
FIGURE 10. Demo Board Schematic
FIGURE 11. PCB Top Layer
FIGURE 12. PCB Bottom Layer
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11 Lead Molded TO-220
LM2402 Monolithic Triple 3 ns CRT Driver National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.