LM1247 National Semiconductor, LM1247 Datasheet - Page 10

• Manufacturer Part Number: LM1247
• 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 Descriptions and Application Information
No.
Pin
10
11
12
13
14
15
16
17
18
8
9
Digital Ground
DAC 4 Output
DAC 2 Output
DAC 3 Output
DAC 1 Output
Pin Name
PLL Filter
PLL V
Ground
SDA
SCL
V
CC
CC
Schematic
10
The ground pin should be connected to the rest
of the circuit ground by a short but independent
PCB trace to prevent contamination by
extraneous signals. The V
isolated from the rest of the V
bead and bypassed to pin 8 with an electrolytic
capacitor and a high frequency ceramic.
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
The I
of about 2 kΩ should be connected between this
pin and V
be connected in series with the data line for
additional ESD protection.
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.
(Continued)
2
2
C compatible data line. A pull-up resistor
C compatible clock line. A pull-up resistor
CC
CC
. A resistor of at least 100Ω should
. A resistor of at least 100Ω should
Description
CC
pin should be
CC
line by a ferrite
2
C, etc.
2
C