LM1246AAA National Semiconductor, LM1246AAA Datasheet - Page 12

• Manufacturer Part Number: LM1246AAA
• Description: 150 MHz I2C Compatible RGB Preamplifier with Internal 512 Character OSD ROM/ 512 Character RAM and 4 DACs
• Manufacturer: National Semiconductor

www.national.com
Pin
No.
12
13
14
15
16
17
18
19
20
21
22
Pin Descriptions and Application Information
DAC 4 Output
DAC 2 Output
DAC 3 Output
DAC 1 Output
Green Output
Blue Output
Red Output
Pin Name
Ground
SCL
V
ABL
CC
Schematic
12
(Continued)
The I
of about 2 kΩ should be connected between this
pin and V
be connected in series with the clock line for
additional ESD protection.
DAC outputs for cathode cut-off adjustments and
brightness control. DAC 4 can be set to change
the outputs of the other three DACs, acting as a
brightness control. The DAC values and the
special DAC 4 function are set through the I
compatible bus. A resistor of at least 100Ω
should be connected in series with these outputs
for additional ESD protection.
Ground pin for the output analog portion of the
LM1247 circuitry, and power supply pin for all
the analog of the LM1247. Note the
recommended charge storage and high
frequency capacitors which should be as close to
pins 17 and 18 as possible.
These are the three video output pins. They are
intended to drive the LM246x family of cathode
drivers. Nominally, about 2V peak to peak will
produce 40V peak to peak of cathode drive.
The Automatic Beam Limiter input is biased to
the desired beam current limit by R
and normally keeps D
the current resupplying the CRT capacitance
(averaged by C
begins to turn off and the voltage at pin 22
begins to drop. The LM1247 then lowers the
gain of the three video channels until the beam
current reaches an equilibrium value.
2
C compatible clock line. A pull-up resistor
CC
. A resistor of at least 100Ω should
ABL
Description
) exceeds this limit, then D
INT
forward biased. When
ABL
and V
2
C
BB
INT