參數(shù)資料
型號(hào)： LM1270
廠商： National Semiconductor Corporation
英文描述： Hi-Brite 200 MHz I2C Compatible RGB Image Enhancer with Video Auto Sizing
中文描述： 高亮度場(chǎng)致200兆赫與I2C兼容的RGB視頻自動(dòng)上漿圖像增強(qiáng)
文件頁(yè)數(shù)： 9/27頁(yè)
文件大?。?/td> 1302K
代理商： LM1270
Functional Description
(Continued)
Using the data encoded on the video eliminates one stage of
communicating with the LM1270, allowing for a faster re-
sponse time for changes in the Hi-Brite window.
V
REF
Proper operation of the LM1270 does require a very accu-
rate reference voltage. This voltage is generated in the V
REF
block. To insure an accurate voltage over temperature, an
external resistor is used to set the current in the V
REF
stage.
The external resistor is connected to pin 23. This resistor
should be 1% and have a temperature coefficient under
100 ppm/C. ALL VIDEO SIGNALS MUST BE KEPT AWAY
FROM PIN 23. This pin has a very high input impedance and
will pick up any high frequency signals routed near it. The
board layout shown in
Figure 12
is a good example of trace
routing near pin 23. The output of the V
stage goes to a
number of blocks in the video section and also to pin 22. This
pin allows capacitor filtering on the V
output and offers an
accurate external reference. A buffer must be used with this
reference, the maximum current loading should be only
100 μA. Pin 22 is bi-directional, allowing the LM1270 to be
referenced to a pre-amp V
. This configuration makes it
possible to DC couple to the pre-amp, but for accurate DC
level, it is recommended that AC coupling be used between
the LM1270 and the pre-amp. It is also recommended that
the internal V
be used for best performance.
Note:
Any
noise injected into pin 22 will appear on the video. The
voltage reference must be kept very clean for best perfor-
mance of the LM1270.
H FLYBACK
H Flyback is an analog signal input from the monitor hori-
zontal scan. This flyback signal goes to the internal horizon-
tal flyback pulse generation circuit. An optional capacitor
and/or resistor to ground may be needed if noise interferes
with the H Flyback signal or if there is ringing on the H
Flyback signal. Note: there is no blanking pedestal on the
output video. If horizontal blanking is to be added to the
video signal it must be done at the pre-amp.
R
LIMIT
is used to limit the input current into the IC to a
maximum value of +1 mA during flyback and 100 μA during
normal forward scan. For example if an H flyback with a peak
of 100V is used, R
= 100 k
. The internal input imped-
ance of pin 16 is low to limit the maximum voltage swing at
the input to be within the supply rail and ground.
Figure 2
shows the H flyback waveforms and the location of R
. A
56 pF capacitor has been added to the H Flyback pin for
filtering noise on the H Flyback signal.
VERTICAL BLANKING
A similar vertical pulse generation circuit to the LM1238 is
included internal to the LM1270. The leading edge of the
vertical sync is used to start the programmable vertical
blanking signal directly. The Vertical Blank Duration Control
Register sets the width of the pulse. When vertical blanking
is enabled its polarity is programmable.
CLAMPING
Pin 24, the clamp pin, can be set for either an input or and
output. If used as an input, then this pin functions just like the
clamp input pins to the video pre-amps. One should use a
series 1 k
resistor to pin 24 and a small capacitor may also
be needed between pin 24 and ground to filter high fre-
quency noise.
20063519
FIGURE 2. H Flyback Input Pulse
L
www.national.com
9
相關(guān)PDF資料
PDF描述
LM1270N Hi-Brite 200 MHz I2C Compatible RGB Image Enhancer with Video Auto Sizing
LM1270NA Hi-Brite 200 MHz I2C Compatible RGB Image Enhancer with Video Auto Sizing
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LM1279N 110 MHz RGB Video Amplifier System with OSD
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LM1270N 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Hi-Brite 200 MHz I2C Compatible RGB Image Enhancer with Video Auto Sizing
LM1270NA 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Hi-Brite 200 MHz I2C Compatible RGB Image Enhancer with Video Auto Sizing
LM1276 制造商:NSC 制造商全稱:National Semiconductor 功能描述:150 MHz I2C Compatible RGB Preamplifier with Internal 512 Character OSD ROM, 512 Character RAM and 4 DACs
LM1276AAA 制造商:NSC 制造商全稱:National Semiconductor 功能描述:150 MHz I2C Compatible RGB Preamplifier with Internal 512 Character OSD ROM, 512 Character RAM and 4 DACs
LM1279 制造商:NSC 制造商全稱:National Semiconductor 功能描述:110 MHz RGB Video Amplifier System with OSD
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