LM1237 Datasheet, PDF (1/42 Pages) National Semiconductor (TI) – 150 MHz I2C Compatible RGB Preamplifier with Internal 254 Character OSD and 4 DACs

September 2002
LM1237
150 MHz I²C Compatible RGB Preamplifier with Internal
254 Character OSD and 4 DACs
General Description
The LM1237 pre-amp is an integrated CMOS CRT preamp.
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. Brightness and bias
can be controlled through the DAC outputs which are well
matched to the LM2479 and LM2480 integrated bias clamp
ICs. The LM1237 preamp is also designed to be compatible
with the LM246x high gain driver family.
Black level clamping of the video signal is carried out directly
on the AC coupled input signal into the high impedance
preamplifier input, thus 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.
The IC is packaged in an industry standard 24 lead DIP
molded plastic package.
Features
n I²C compatible microcontroller interface
n Internal 254 character OSD usable as either (a) 190
2-color plus 64 4-color characters, (b) 318 2-color
characters, or (c) some combination in between.
n OSD override allows OSD messages to override video
and the use of burn-in screens with no video input
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 80% power reduction
n Matched to LM246x driver and LM2479/80 drivers
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 LM1237AAF/NA
See NS Package Number N24D
© 2002 National Semiconductor Corporation DS200234
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