LM2467 datasheet(7/43 Pages) NSC

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Compatibility with LM1237 and LM1247 (Continued)

TABLE 2. LM1253A/LM1237 Compatibility

DAC Bias Outputs

LM1236 Pin:

DAC 1

DAC 2

DAC 3

DAC 4

Assignment:

Blue

Green

Red

Brightness

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

tradeoff allows fine tuning the final OSD intensity relative to

the video. In addition, the OSD contrast register, 0x8438

[4:3], provides 4 major increments of intensity. Together,

these allow setting the OSD intensity to the most pleasing

level.

ESD Protection

The LM1236 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. At that time, the protection is

applied to all the pins, including SDA and SCL.

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