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參數(shù)資料
| 型號(hào)： | LM1238AAF/NA |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | 3 CHANNEL, VIDEO PREAMPLIFIER, PDIP24 |
| 封裝： | N24D |
| 文件頁數(shù)： | 23/24頁 |
| 文件大?。?/td> | 1207K |
| 代理商： | LM1238AAF/NA |
Pin Descriptions and Application Information
Pin
No.
Pin Name
Schematic
Description
1
V Flyback
Required for OSD synchronization and is also
used for vertical blanking of the video outputs.
The actual switching threshold is about 35% of
V
CC. For logic level inputs C4 can be a jumper,
but for flyback inputs, an AC coupled
differentiator is recommended, where R
V is large
enough to prevent the voltage at pin 1 from
exceeding V
CC or going below GND. C4 should
be small enough to flatten the vertical rate ramp
at pin 1. C
24 may be needed to reduce noise.
2V
REF Bypass
Provides filtering for the internal voltage which
sets the internal bias current in conjunction with
R
EXT. A minimum of 0.1 F is recommended for
proper filtering. This capacitor should be placed
as close to pin 2 and the pin 4 ground return as
possible.
3V
REF Current Set
External resistor, 10k 1%, sets the internal bias
current level for optimum performance of the
LM1238. This resistor should be placed as close
to pin 3 and the pin 4 ground return as possible.
4
Analog Ground
This is the ground for the analog portions of the
LM1238 internal circuitry.
5
6
7
Blue Video In
Red Video In
Green Video In
These video inputs must be AC coupled with a
.0047 F cap. Internal DC restoration is done at
these inputs. A series resistor of about 33
and
external ESD protection diodes should also be
used for protection from ESD damage.
8
10
PLL Ground
PLL V
CC
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
CC pin should be
isolated from the rest of the V
CC line by a ferrite
bead and bypassed to pin 8 with an electrolytic
capacitor and a high frequency ceramic.
LM1238
www.national.com
8
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