LM1253A National Semiconductor, LM1253A Datasheet

LM1253A

Manufacturer Part Number

LM1253A

Description

Monolithic Triple 180 MHz I2C CRT Pre-amp With Integrated Analog On Screen Display (OSD) Generator

Manufacturer

National Semiconductor

Datasheet

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LM1253A

Monolithic Triple 180 MHz I

Integrated Analog On Screen Display (OSD) Generator

General Description

The LM1253A pre-amp is an integrated high voltage triple

CRT pre-amp and Analog On Screen Display (OSD) genera-

tor. The IC is I

rameters necessary to setup and adjust the brightness and

contrast in the CRT display. In addition, it provides a pro-

grammable 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 se-

lection of colors. The preset level of the OSD can be con-

trolled by I

is internally mixed with the video signal, before the gain sec-

tion, 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 ex-

cellent white color point tracking with variations in the Bright-

ness control. An active horizontal blanking signal is added to

the video at the output, giving excellent smear performance,

and preventing video content dependent DC bias offsets as

a result of high frequency over shoot.

The OSD horizontal sync and blanking signal is derived from

a positive going flyback pulse. The digital section provides

easy interfacing of this signal with the deflection circuits.

The vertical blanking signal is taken from the vertical sync

signal, and the blanking duration is programmable. This sys-

tem is highly integrated and requires a minimal number of

external components.

Black level clamping of the signal is carried out directly on

the AC coupled input signal into the high impedance pream-

plifier input, thus eliminating the need for additional black

level clamp capacitors.

C to suit different CRT displays. The OSD signal

C controlled, and allows control of all the pa-

DS101265

C CRT Pre-amp With

The outputs are referenced to a DC level produced by the

LM1253A Pre-amp, and so are guaranteed to provide stable

DC operating levels within the system without the need for

additional external feedback components.

The IC is packaged in an industry standard wide body 28-

lead DIL molded plastic package.

Features

n 190 two-color ROM based Character Fonts

n 64 four-color ROM based Character Fonts

n Supports a programmable page size with up to 512

n Support for 2 Display Windows (size of each window is

n Programmable start position for each Display Window

n Programmable Resolutions: from 512 to 960 pixels per

n Programmable Character Height, with automatic height

n Programmable Row Spacing between each display

n Maximum Pixel clock of 92.2 MHz

n I

n Button boxes

n 180 MHz preamplifier with full video signal parametric

n VideoPlex

n OSD mixing with 64 out of 512 color mask

Intended Applications

n 1280 x 1024 Displays up to 75 Hz requiring OSD

characters and line definition codes

configurable)

line in 64 pixel increments

control with mode change

character row

control

programmable selection

capability

C compatible interface to controlling micro-controller

™

interface to the LM2453 driver

www.national.com

May 2000

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