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参数资料
| 型号： | LM1253AAE/NA |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 画面叠加 |
| 英文描述： | ON-SCREEN DISPLAY IC, PDIP28 |
| 封装： | 0.600 INCH, PLASTIC, DIP-28 |
| 文件页数： | 9/61页 |
| 文件大小： | 1671K |
| 代理商： | LM1253AAE/NA |
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ESD and Arc-Over Protection
(Continued)
Output signal traces of the LM1253A (video, V
BLANK,
V
REF) should be kept away from traces that carry the
output signals of the LM2453.
If any one of the above suggestions is not followed the
LM1253A may become more vulnerable to arc-over. Im-
proper grounding is by far the most common cause of a
video pre-amp failure during arc-over.
The I
2C specification recommends that the SDA and SCL
pins should be protected from arc-over. This is done by
adding a resistor in series with each pin.
Figure 27 shows
how the resistors are connected to the SDA and SCL lines.
Pre-Amp Functional Description
Figure 1 shows the block diagram of the LM1253A. The
video signal is input to the LM1253A through the circuit
shown in
Figure 26. Black level clamping is carried out
directly on the AC coupled input signal at the input of the high
impedance buffer amplifier, thus eliminating the need for
black level clamp capacitors. The following sections then
modify the input video signal:
Contrast Attenuator — Sets the contrast level of the video
signal for all three channels.
Auto Beam Limit — Reduces the gain of all three video
amplifiers in response to a control voltage proportional to
the CRT beam current.
Gain Attenuator — Separately sets the gain for each
video channel.
Brightness — Sets the brightness for all three channels.
Bias — Adds an offset to the brightness controls for all
three video channels.
Pedestal — Adds a dc voltage offset to the brightness
control, in order that bi-directional control of the bright-
ness control is always possible at all bias voltage set-
tings.
Source Select — Switches between the input video signal
and the analog OSD signal generated by the 3 bit pallet
DAC control block.
DC Offset — Adds a dc voltage offset to all three video
outputs.
The above sections use the registers shown in
Table 2.
Figure 28 shows which section of the output video and clamp
signal each register controls.
DS101265-29
FIGURE 26. Recommended Video Input ESD Protection
DS101265-30
FIGURE 27. Recommended Arc-Over Protection for
SDA and SCL Pins
LM1253A
www.national.com
17
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| LM1267NA/NOPB | 3 CHANNEL, VIDEO PREAMPLIFIER, PDIP24 |
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| LM1276AAA/NA | 1 CHANNEL, VIDEO PREAMPLIFIER, PDIP28 |
| LM1279AN/NOPB | 3 CHANNEL, VIDEO AMPLIFIER, PDIP20 |
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM1253AN | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Monolithic Triple 180 MHz I2C CRT Pre-amp With Integrated Analog On Screen Display (OSD) Generator |
| LM-1256 | 制造商:ROHM 制造商全称:Rohm 功能描述:16 x 16 matrix displays |
| LM-1256_1 | 制造商:ROHM 制造商全称:Rohm 功能描述:16】16 matrix displays |
| LM-1256LB1 | 制造商:ROHM 制造商全称:Rohm 功能描述:16】16 matrix displays |
| LM125AN | 制造商:NSC 制造商全称:National Semiconductor 功能描述:VOLTAGE REGULATORS |
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