The LM1253A pre-amp is an integrated high voltage triple CRT pre-amp and Analog On Screen Display (OSD) generator. The IC is I2C controlled, and allows control of all the parameters necessary to setup and adjust the brightness and contrast in the CRT display. In addition, it provides a programmable period vertical blanking pulse which is used to blank the G1. The LM1253A pre-amp is designed to work in cooperation with the LM2453 driver, and provides a multiplexed video signal (VideoPlex) interface to enable the DC clamp levels at the cathode to be varied in order to set up the CRT bias and to allow individual adjustment for brightness. The Analog OSD has a selectable palette allowing a wide selection of colors. The preset level of the OSD can be controlled by I2C to suit different CRT displays. The OSD signal is internally mixed with the video signal, before the gain section, and thus gives excellent white tracking of the OSD with the white color point setting of the video. The Brightness settings are also mixed into the video signal before the gain matching controls and consequently give excellent white color point tracking with variations in the Brightness control. An active horizontal blanking signal is added to the video at the output, giving excellent smear performance, and preventing video content dependency
The LM1253A is a monolithic triple 180 MHz CRT pre‑amplifier with an integrated analog on‑screen‑display (OSD) generator. It provides I²C‑controlled brightness and contrast adjustment, programmable vertical blanking, and a VideoPlex interface for bias control, all in a 28‑lead wide‑body DIL package.
Key features include two‑color and four‑color ROM character fonts, programmable display windows, up to 960‑pixel line resolution, and extensive programmable parameters such as OSD palette, pixel clock, and blanking levels. The datasheet provides detailed electrical characteristics, pin descriptions, test settings, and interface diagrams for system integration.
| Maximum pixel clock | 92.2 MHz |
|---|---|
| Maximum supply current | 245 mA |
| Package type | 28‑lead wide‑body DIL |
The maximum pixel clock is 92.2 MHz.
It supports 190 two‑color ROM based character fonts and 64 four‑color ROM based character fonts.
It is supplied in a 28‑lead wide‑body DIL molded plastic package.
The maximum supply current is 245 mA under no load.