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參數(shù)資料
| 型號： | LMH1251 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | YPBPR to RGB Decoder and 2:1 Video Switch |
| 中文描述： | 色差到RGB解碼器和2:1視頻開關(guān) |
| 文件頁數(shù)： | 7/10頁 |
| 文件大小： | 614K |
| 代理商： | LMH1251 |
Application Notes
GENERAL INFORMATION
The LMH1251 is a high-speed triple 2:1 video multiplexer
with an integrated sync processor and color space converter.
One input channel accepts standard RGBHV PC graphics
video and the second input channel accepts YP
B
P
R
compo-
nent video. If the first input of the MUX is selected, the
device will output the RGBHV video from the input with unity
gain. If the second input of the MUX is selected, sync pro-
cessing and color space conversion will be performed on the
YP
B
P
R
component signals to provide an equivalent RGBHV
signal at the output.
YP
B
P
R
to RGBHV PROCESSING
The LMH1251 is capable of processing 480i, 480p, 576i,
576p, 720p, 1080i, and 1080p/60 YP
P
component video
signals only. S-Video, composite NTSC, or composite PAL
video will not be decoded by the LMH1251. For High Defini-
tion, 720p and 1080i video, the LMH1251 will decode the
luminance and color difference signals into primary RGB
signals according to the linear arithmetic formula specified in
the EIA/CEA-770.3-C Standard for High Definition Analog
Component TV. For Standard Definition video, the LMH1251
will perform the decoding according to the linear arithmetic
formula specified in the EIA/CEA-770.2-C Standard for Stan-
dard DefinitionAnalog Component TV. The advanded analog
architecture that is employed to perform the color space
conversion is precise to within 2.5% of amplitude & 1.5 of
phase error on a vectorscope with a color bar test signal.
This is illustrated with a vectorscope plot of a decoded color
bar signal in the 720p format show in the Typical Perfor-
mance Characteristics section.
Note that although 480i/576i component video is supported
by the LMH1251, most PC Display Monitors cannot handle
such line rates. Typically, only 480p, 576p, 720p, and 1080i/
1080p are within the displayable line rate range of LCD and
CRT monitors. Furthermore, the scaler in LCD monitor sys-
tems must include a de-interlacer for it to display interlaced
video such as with 1080i.
Component Video Formats supported by the
LMH1251
480i
480p
576i
576p
720p
1080i23/25/30
1080p50/59/60
AUTO/MANUAL FORMAT DETECTION
The LMH1251 can either automatically detect the input for-
mat of the component video source, or it can be put in a
manual mode where the MCU has the flexibility to specify
which YP
P
to RGBHV processing scheme for the device
to apply depending on the input format. If a logic high is
applied to Pin 23, the LMH1251 will be in the AUTO detec-
tion mode, which is typically recommended. In this mode, the
device will appropriately use the correct YP
P
to RGBHV
processing scheme based on its input format detection. If a
logic high is applied to Pin 23, the LMH1251 will be in the
Manual detection mode. In this mode, the MCU must apply a
logic low to Pin 22 if the processing scheme is for SD Video
formats, and a logic high if the processing scheme is for HD
Video formats.
Note that in the AUTO mode, Pin 22 becomes an output pin,
and outputs a logic low if a SD video input is detected and a
logic high if a HD video input is detected, as notification to
the MCU.
MACROVISION COMPATIBILITY
The on-chip sync processor of the LMH1251 is fully compat-
ible with DVD video sources which are embedded with Mac-
rovision copyright protection. The LMH1251 will output Hori-
zontal Sync pulses with consistent periodicity even during
the “Macrovision Sync” pulse period.
POWER SAVE MODE
The LMH1251 is equipped with a power saving mode which
is controlled by Pin 21. This pin is a logic level input. The
device will enter a low power mode when the power save pin
is applied with a logic high by the MCU. Under these condi-
tions, the IC reduces its current consumption to a minimum
as specified in the Electrical Characteristics section. How-
ever, the sync processor and switch will always remain
active. During power save mode, the RGB video outputs are
held to the blank level, while the sync signals are allowed to
continue to be processed and/or passed through. Based on
the absence or presence of sync signals at the output of the
LMH1251, the MCU can determine whether to bring the
system to a low power consumption state.
OUTPUT DRIVE CHARACTERISTICS
The LMH1251 is designed to interface with an ADC or
preamplifier through an AC coupling capacitor as shown
below in
Figure 1
. The RGB outputs of the LMH1251 are 700
mV
video signals with the black level at approximately 2V,
which is the chip’s internal voltage reference level. The H
Sync and V Sync outputs are CMOS logic outputs that swing
from 0 to 5V. These RGBHV outputs do not have any current
drive capability and should not have any load on them. The
PCB trace length at the output should be kept as short as
possible to minimize resisitive and capacitive loading.
If the LMH1251 is to be designed into a stand-alone con-
verter box application, the configuration in
Figure 2
is rec-
ommended. The LMH6739, triple op amp with an internally
set gain of 2, can be used to drive RGB video over the VGA
cable out to a display monitor. Logic inverters are used for
driving the sync signals over the VGA cable.
L
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相關(guān)PDF資料 |
PDF描述 |
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| LMH1251MT | YPBPR to RGB Decoder and 2:1 Video Switch |
| LMH1251MTX | YPBPR to RGB Decoder and 2:1 Video Switch |
| LMH6502 | Wideband, Low Power, Linear-in-dB Variable Gain Amplifier |
| LMH6502MA | Wideband, Low Power, Linear-in-dB Variable Gain Amplifier |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LMH1251EVAL | 制造商:Texas Instruments 功能描述:Evaluation Board For LMH1251 Analog Video Switch 制造商:OC White Company 功能描述:Evaluation Board For LMH1251 Analog Video Switch |
| LMH1251EVAL/NOPB | 功能描述:視頻 IC 開發(fā)工具 LMH1251 EVAL BOARD RoHS:否 制造商:Texas Instruments 產(chǎn)品:Evaluation Boards 類型:YPbPr to RGBHV Converters 工具用于評估:LMH1251 工作電源電壓:5 V |
| LMH1251MT | 功能描述:視頻開關(guān) IC RoHS:否 制造商:Texas Instruments 開關(guān)數(shù)量:4 開啟電阻（最大值）:12 Ohms 傳播延遲時間: 開啟時間（最大值）: 關(guān)閉時間（最大值）: 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:WQFN-42 封裝:Reel |
| LMH1251MT/NOPB | 功能描述:視頻開關(guān) IC RoHS:否 制造商:Texas Instruments 開關(guān)數(shù)量:4 開啟電阻（最大值）:12 Ohms 傳播延遲時間: 開啟時間（最大值）: 關(guān)閉時間（最大值）: 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:WQFN-42 封裝:Reel |
| LMH1251MT-NOPB | 制造商:TI 制造商全稱:Texas Instruments 功能描述:YPBPR Path: 70 MHz, a??3 dB, 700 mVPP Bandwidth |
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