LM1276 National Semiconductor Corporation, LM1276 Datasheet - Page 9

• Manufacturer Part Number: LM1276
• Description: 150 Mhz I2c Compatible Rgb Preamplifier With Internal 512 Character Osd Rom, 512 Character Ram And 4 Dacs
• Manufacturer: National Semiconductor Corporation

OSD vs Video Intensity
The OSD amplitude has been increased over the LM1237
level. During monitor alignment the three gain registers are
used to achieve the desired front of screen color balance.
This also causes the OSD channels to be adjusted accord-
ingly, since these are inserted into the video channels prior
to the gain attenuators. This provides the means to fine-tune
the intensity of the OSD relative to the video as follows. If a
typical starting point for the alignment is to have the gains at
maximum (0x7F) and the contrast at 0x55, the resultant
OSD intensity will be higher than if the starting point is with
the gains at 0x55 and the contrast at maximum (0x7F). This
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tradeoff allows the fine-tuning of the final OSD intensity
relative to the video. In addition, the OSD contrast register,
0x85C8[5:3], provides 8 major increments of intensity. To-
gether, these allow setting the OSD intensity to the most
pleasing level.
ESD Protection
The LM1276 features a 3.0 kV ESD protection level (see
(Notes 4, 13)). This is provided by special internal circuitry,
which activates when the voltage at any pin goes beyond the
supply rails by a preset amount. This protection is applied to
all the pins, including SDA and SCL.
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