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參數資料
| 型號： | LM1276AAA/NA |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | 1 CHANNEL, VIDEO PREAMPLIFIER, PDIP28 |
| 封裝： | PLASTIC, DIP-28 |
| 文件頁數： | 10/50頁 |
| 文件大小： | 6075K |
| 代理商： | LM1276AAA/NA |
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Burn In Screen
The LM1276 provides a Burn In Screen feature, where a full
screen of white video will be displayed without the need for
any video input. The Burn In Screen is enabled by setting bit
5 of register 0x8439 to 1. The contrast level of this Burn In
display can be adjusted with a 2 Bit DAC over the range of
65% to 85% of normal white level video. This adjustment is
made with register 0X8439[7:6].
Programmable Horizontal Blank
The leading edge position of the internal horizontal blank can
be programmed with respect to the horizontal flyback zero
crossing leading edge in steps of 1 OSD pixel up to a maxi-
mum of 31 steps as shown below in Figure 12. This start
position of the horizontal blanking pulse is only programmable
to occur before the horizontal flyback zero crossing edge, and
cannot be programmed in the opposite direction. The trailing
edge of the horizontal blanking pulse is independent of the
programmable leading edge, and its relativity to the Horizon-
tal flyback trailing edge remains unchanged. To use this
feature, both Horizontal Blanking (0x843A[0]) and Pro-
grammable Horizontal Blanking (0x843A[2]) must be en-
abled. The number of steps is programmed with the bits in
0x843A[7:3]
. When this feature is disabled, please refer to
the H-Blank Time Delay – On specification (+ Zero Crossing
of I
HFB to 50% of output blanking end) listed under the System
Interface Signal Characteristics section.
20096952
FIGURE 12. Programmable Internal H. Blank
Video Detection for Auto-Sizing &
Auto-Centering
The LM1276 is capable of taking measurements necessary
for the monitor’s microcontroller to perform the auto-sizing
and auto-centering operations. The horizontal and vertical
flybacks/syncs are used as the reference for timing. Either the
flyback or sync signals may be used. In this section, the fly-
back signals will be considered, although horizontal and ver-
tical sync can be applied similarly. The resultant outputs are
the flyback time, the position of the start of video relative to
the flyback end, and the time from the end of the active video
to the start of the flyback time. Since the total line time is
known, the microcontroller can calculate the active video
time. The microcontroller can center the video between the
start and end of flyback for best image centering, and to cal-
culate the duty cycle of the video with respect to the forward
scan time, thus giving a measure of the relative size of the
image.
VIDEO INPUT DETECTION
The LM1276 will detect even low-level video information to
determine the video image size and position. The video detect
logic must also find the extreme points of the displayed image
during each frame with respect to the horizontal and vertical
flyback pulses as measured using the internal PLL. For best
performance in the auto-sizing mode, it is recommended that
the application use the maximum pixels per line mode is used
when measurements are made. The durations to be mea-
sured are shown generically in Figure 13 and apply to both
horizontal and vertical timings. Since measurements are
made in terms of OSD pixels, the ratio of OSD pixels per
line to the video pixels per line must be applied to the data
below to attain measurements in terms of video pixels.
1.
Flyback or sync period: The duration of either the sync
input or the horizontal flyback, in either horizontal lines
(vertical) or pixels (horizontal).
2.
Back porch period: The duration between the trailing
edge of the sync or flyback pulse and the leading edge
of the first detected video, in either lines (vertical) or
pixels (horizontal).
3.
Front porch: The duration between the trailing edge of
the last detected video and the leading edge of the sync
or flyback pulse, in either lines (vertical) or pixels
(horizontal).
The video period is the duration between the leading edge of
the first detected video and the trailing edge of the last de-
tected video, in either lines (vertical) or OSD pixels (horizon-
tal). This period is calculated by the microcontroller with the
measured periods above.
As the video may start and finish at different positions on the
screen, depending upon the image, the measured horizontal
porches and video time may vary from line to line. To over-
come this, the periods should be measured over at least one
entire field. The hardware records the shortest back porch
and front porch periods used over the measured period. The
possible error for the above measurements are within 1 to 2
OSD pixels.
The video period is the duration between the leading edge of
the first detected video and the trailing edge of the last de-
tected video, in either lines (vertical) or OSD pixels (horizon-
tal). This period is calculated by the microcontroller with the
measured periods above.
The analog front end video detection is also utilized by the
Video Data Interface for decoding of color bar data. It is crit-
ical to note again that the threshold for video detection
is 80mV above the internal V
REF voltage, and also the
minimum rise time requirement of the driving PC video
card must be at least 10.0ns.
Excessively slow rise times in
the PC video card will prevent the video detect circuit from
working properly.
To perform an auto size calculation, the following instruction
sequence must be done by the MCU:
www.national.com
18
200969 Version 2 Revision 4
Print Date/Time: 2011/07/11 11:20:12
LM1276
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LM1279 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:110 MHz RGB Video Amplifier System with OSD |
| LM12791DL WAF | 制造商:Texas Instruments 功能描述: |
| LM1279A | 制造商:未知廠家 制造商全稱:未知廠家 功能描述: |
| LM1279AN | 功能描述:IC AMP RGB VIDEO SYSTEM 20-DIP RoHS:否 類別:集成電路 (IC) >> 線性 - 放大器 - 視頻放大器和頻緩沖器 系列:- 標準包裝:1,000 系列:- 應用:驅動器 輸出類型:差分 電路數:3 -3db帶寬:350MHz 轉換速率:1000 V/µs 電流 - 電源:14.5mA 電流 - 輸出 / 通道:60mA 電壓 - 電源，單路/雙路(±):5 V ~ 12 V，±2.5 V ~ 6 V 安裝類型:表面貼裝 封裝/外殼:20-VFQFN 裸露焊盤 供應商設備封裝:20-QFN 裸露焊盤（4x4） 包裝:帶卷 (TR) |
| LM1279DL WAF | 制造商:Texas Instruments 功能描述: |
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