LM1236 National Semiconductor Corporation, LM1236 Datasheet - Page 11

• Manufacturer Part Number: LM1236
• Description: 150 Mhz I2c Compatible Rgb Preamplifier With Internal 254 Character Osd Rom, 512 Character Ram And 4 Dacs
• Manufacturer: National Semiconductor Corporation

Pin
No.
10
11
Pin Descriptions and Application Information
3
4
5
6
7
8
9
Green Video In
Digital Ground
Blue Video In
Red Video In
Analog Input
Digital V
Pin Name
PLL Filter
Ground
V
SDA
REF
CC
Schematic
11
(Continued)
External resistor, 10k 1%, sets the internal bias
current level for optimum performance of the
LM1247. This resistor should be placed as close
to pin 3 and the pin 4 ground return as possible.
This is the ground for the input analog portions
of the LM1247 internal circuitry.
These video inputs must be AC coupled with a
.0047 µF cap. Internal DC restoration is done at
these inputs. A series resistor of about 33Ω and
external ESD protection diodes should also be
used for protection from ESD damage.
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.
2
C compatible data line. A pull-up resistor
CC
. A resistor of at least 100Ω should
Description
CC
pin should be
CC
line by a ferrite
2
C, etc.
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