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参数资料
| 型号： | LM1276AAA/NA |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 音频／视频放大 |
| 英文描述： | 1 CHANNEL, VIDEO PREAMPLIFIER, PDIP28 |
| 封装： | PLASTIC, DIP-28 |
| 文件页数： | 3/50页 |
| 文件大小： | 6075K |
| 代理商： | LM1276AAA/NA |
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VIDEO PROCESSING
Emphasis, Center Frequency at Maximum
20096963
Center Frequency, Emphasis at Maximum
20096964
These two plots show the processing done by the LM1276 on
the video input signal. There are two variables for the video
processing, emphasis and center frequency. Emphasis is
controlled by bits 0-2 in registers 0x85C8, 0x85CA, or
0x85CC.
This gives 8 different levels of emphasis. In the top
plot the center frequency is set at its maximum level and the
8 different levels of emphasis are measured. The video with
no emphasis is adjusted to a 0.7 V
P-P level. Using maximum
emphasis the video is increased to a 0.9 V
P-P level at the rising
edge of the video. If the falling edge was measured it would
show a similar waveform, but going in the negative direction.
Center frequency is shown in the bottom plot. Control of the
center frequency is done with bits 4-7 in register
0x85C1
. This gives 16 adjustments for this feature. Every
other adjustment is shown in the bottom plot, since showing
all 16 adjustments would have made the plot too difficult to
read. The curves closely approximate the peaking of an RC
network. Therefore, the term center frequency means the RC
time constant that is approximated by each curve in the above
plot. A true RC peaking network would give very large over-
shoot. The LM1276 has special circuitry to clip the very large
overshoot, yet has the complete benefit of the RC peaking.
This special circuitry allows for much more overshoot than
one could do with RC peaking and still not saturate the video
channel.
Note that the video channel with the emphasis also has its
own independent contrast control. This allows the user to ad-
just his monitor for a brighter picture within the Hi-Brite win-
dow and optimize the emphasis for the resolution he is using
with the monitor. Now, the monitor user can give his pictures
or video a special “sparkle” when using the capabilities of the
LM1276.
OSD PHASE LOCKED LOOP
The PLL in the LM1276 serves both the OSD as well as the
Hi-Brite Window generation. The pixels per line range for the
LM1276 OSD is from 704 to 1152 pixels per line, in incre-
ments of 64. The maximum OSD pixel frequency available is
111 MHz. For example, if the horizontal scan rate is 106 kHz,
1024 pixels per line would be acceptable to use, since the
OSD pixel frequency is:
Horizontal Scan Rate X PPL =
106kHz X 1024 = 108.5 MHz
If 1152 pixels per line is being used, the horizontal scan rate
would have to be lower than 106 kHz in order to not exceed
the maximum OSD pixel frequency of 111 MHz. The maxi-
mum number of video lines that may be used is 1536 lines as
in a 2048x1536 display. At this line rate, using a PPL setting
of 4 is recommended. The LM1276 has a PLL Auto feature,
which will automatically select an internal PLL frequency
range setting that will guarantee optimal OSD locking for any
horizontal scan rate and for improved jitter performance over
a wider temperature range. This eliminates the need for PLL
register settings determined by the user, as well as improved
PLL performance. To initialize the PLL Auto feature, set bit,
0x8439[4] to 1. This will effectively perform all necessary cal-
ibrations and activate the PLL Auto mode, which takes ap-
proximately 2–4 vertical scan period to complete, and must
be done while the video is blanked. Table 2 shows the rec-
ommended horizontal scan rate ranges (in kHz) for each
pixels per line register setting, 0x8401[7:5]. These ranges are
recommended for chip ambient temperatures of 0C to 70C,
and the recommended PLL filter values are 6.2 k
, 0.01 uF,
and 1000 pF. While the OSD PLL will lock for other register
combinations and at scan rates outside these ranges, the
performance of the loop will be improved if these recommen-
dations are followed.
PLL AUTO MODE INITIALIZATION SEQUENCE
Blank video.
Set 0x8539[4] to 1.
Wait for at least 2–4 vertical periods or vertical sync pulses
to pass.
Unblank Video.
This sequence must be done by the microcontroller at system
power up, as well as each time there is a horizontal line rate
change from the video source, for the PLL Auto mode to func-
tion properly.
TABLE 2. OSD Register Recommendations
PPL=0
PPL=1
PPL=2
PPL=3
PPL=4
PPL=5
PPL=6
PPL=7
PLL Auto
25 - 61
25 - 53
25 - 98
25 - 110
25 - 108
25 - 102
25 - 96
11
www.national.com
200969 Version 2 Revision 4
Print Date/Time: 2011/07/11 11:20:12
LM1276
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM1279 | 制造商:NSC 制造商全称: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:未知厂家 制造商全称:未知厂家 功能描述: |
| LM1279AN | 功能描述:IC AMP RGB VIDEO SYSTEM 20-DIP RoHS:否 类别:集成电路 (IC) >> 线性 - 放大器 - 视频放大器和频缓冲器 系列:- 标准包装:1,000 系列:- 应用:驱动器 输出类型:差分 电路数:3 -3db带宽:350MHz 转换速率:1000 V/µs 电流 - 电源:14.5mA 电流 - 输出 / 通道:60mA 电压 - 电源，单路/双路(±):5 V ~ 12 V，±2.5 V ~ 6 V 安装类型:表面贴装 封装/外壳:20-VFQFN 裸露焊盘 供应商设备封装:20-QFN 裸露焊盘（4x4） 包装:带卷 (TR) |
| LM1279DL WAF | 制造商:Texas Instruments 功能描述: |
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