Pin Descriptions and Application Information (Continued)
Pin
No.
Pin Name
Schematic
Description
9
PLL Filter
Recommended topology and values are shown
to the left. It is recommended that both filter
branches be bypassed to the independent
ground as close to pin 8 as possible. Great care
should be taken to prevent external signals from
coupling into this filter from video, I
2C, etc.
11
SDA
The I
2C compatible data line. A pull-up resistor
of about 2 Kohms should be connected between
this pin and V
CC. A resistor of at least 100
should be connected in series with the data line
for additional ESD protection.
12
SCL
The I
2C compatible clock line. A pull-up resistor
of about 2 k
should be connected between this
pin and V
CC. A resistor of at least 100
should
be connected in series with the clock line for
additional ESD protection.
13
14
15
16
DAC 4 Output
DAC 2 Output
DAC 3 Output
DAC 1 Output
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
2C
compatible bus. A resistor of at least 100
should be connected in series with these outputs
for additional ESD protection.
17
18
Ground
V
CC
Ground pin for the digital portion of the LM1238
circuitry, and power supply pin for both analog
and digital sections of the LM1238. Note the
recommended charge storage and high
frequency capacitors which should be as close
to pins 17 and 18 as possible.
19
20
21
Green Output
Red Output
Blue Output
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.
LM1238
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