LM1238 Datasheet, PDF (1/24 Pages) National Semiconductor (TI) – 110 MHz I2C Compatible RGB Preamplifier with Internal Simple OSD Generator and 4 DACs

June 2003
LM1238
110 MHz I²C Compatible RGB Preamplifier with Internal
Simple OSD Generator and 4 DACs
General Description
The LM1238 pre-amp is an integrated, three channel video
pre-amp. It has an I2C compatible interface which allows
control of all the parameters necessary to directly setup and
adjust the gain and contrast in the CRT display. Four I2C
compatible DACs are available to control monitor bias and
brightness circuits. The LM1238 preamp is designed to be
100% compatible with the LM246x high gain driver family
and the LM2479/80 Clamp ICs.
Black level clamping of the video signal is carried out directly
on the AC coupled input signal into the high impedance
pre-amplifier inputs, eliminating the need for additional
clamp capacitors. Horizontal and vertical blanking of the
outputs is provided. Vertical blanking is optional and its
duration is register programmable.
Features
n I²C compatible microcontroller interface
n Internal OSD generator with 16 sets of color icons
n OSD override allows OSD messages to be displayed
while blanking input video
n Internally generated burn-in screen
n 4 DAC outputs (8-bit resolution) for bus controlled CRT
bias and brightness
n Spot killer which blanks the video outputs when V_CC
falls below the specified threshold
n Suitable for use with discrete or integrated clamp, with
software configurable brightness mixer
n H and V blanking (V blanking is optional and has
register programmable width)
n Power Saving Mode with 65% power reduction
n Matched to LM246x driver and 2479/80 clamp
Applications
n Low end 15" and 17" bus controlled monitors with OSD
n 1024x768 displays up to 85 Hz requiring OSD capability
n Very low cost systems with LM246x driver
Block and Connection Diagram
FIGURE 1. Order Number LM1238AAC/NA
See NS Package Number N24D
20038701
© 2003 National Semiconductor Corporation DS200387
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