LM2412 NSC | Alldatasheet

Document overview

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Technical content

Features

n Rise/fall times typically 2.8 ns with 8 pF load at 40 VPP n Lower power than LM2402 with the same bandwidth 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 with 85 Hz refresh rate n Pixel clock frequency up to 200 MHz Schematic and Connection Diagrams DS101298-1 FIGURE 1. Simplified Schematic Diagram

Application Hints(Continued)

  • C46 and C77-V CC bypass capacitors, near LM2412 and VCC clamp diodes. Very important for arc protection. (Fig- ure 11) The routing of the LM2412 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 LM2412 to the blue 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 LM2412 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 LM2412 during an arc-over event. Lastly, notice that S3 is placed very close to the blue cathode and is tied directly to CRT ground. LM2412 www.national.com 6

FIGURE 10. Demo Board Schematic

FIGURE 11. PCB Top Layer

FIGURE 12. PCB Bottom Layer

Physical Dimensionsinches (millimeters) unless otherwise noted LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. National Semiconductor Corporation Americas Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: support@nsc.com National Semiconductor Europe Fax: +49 (0) 1 80-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 1 80-530 85 85 English Tel: +49 (0) 1 80-532 78 32 Français Tel: +49 (0) 1 80-532 93 58 Italiano Tel: +49 (0) 1 80-534 16 80 National Semiconductor Asia Pacific Customer Response Group Tel: 65-2544466 Fax: 65-2504466 Email: sea.support@nsc.com National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507 www.national.com

11 Lead Molded TO-220

LM2412 Monolithic Triple 2.8 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.