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參數(shù)資料
| 型號： | LM2471 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Monolithic Triple 4 ns High Swing CRT Driver |
| 中文描述： | 單片三重4納秒高秋千CRT顯示器驅(qū)動 |
| 文件頁數(shù)： | 6/10頁 |
| 文件大?。?/td> | 663K |
| 代理商： | LM2471 |
Application Hints
(Continued)
OPTIMIZING TRANSIENT RESPONSE
Referring to
Figure 9
, there are three components (R1, R2
and L1) that can be adjusted to optimize the transient re-
sponse of the application circuit. Increasing the values of R1
and R2 will slow the circuit down while decreasing over-
shoot. Increasing the value of L1 will speed up the circuit as
well as increase overshoot. It is very important to use induc-
tors with very high self-resonant frequencies, preferably
above 300 MHz. Ferrite core inductors from J.W. Miller
Magnetics (part # 78FR--k) were used for optimizing the
performance of the device in the NSC application board. The
values shown in
Figure 11
can be used as a good starting
point for the evaluation of the LM2471. Using a variable
resistor for R1 will simplify finding the value needed for
optimum performance in a given application. Once the opti-
mum value is determined, the variable resistor can be re-
placed with a fixed value.
EFFECT OF LOAD CAPACITANCE
Figure 8
shows the effect of increased load capacitance on
the speed of the device. This demonstrates the importance
of knowing the load capacitance in the application.
EFFECT OF OFFSET
Figure 7
shows the variation in rise and fall times when the
output offset of the device is varied from 50 to 60 V
. The
rise time shows a maximum variation relative to the center
data point (55 V
) of 15%. The fall time shows a variation of
less than 4% relative to the center data point.
THERMAL CONSIDERATIONS
Figure 4
shows the performance of the LM2471 in the test
circuit shown in
Figure 2
as a function of case temperature.
The figure shows that the rise and fall times of the LM2471
increase by approximately 10% as the case temperature
increases from 50C to 100C. This corresponds to a speed
degradation of 2% for every 10C rise in case temperature.
Figure 6
shows the maximum power dissipation of the
LM2471 vs. Frequency when all three channels of the device
are driving an 8 pF load with a 40 V
P-P
alternating one pixel
on, one pixel off signal. The graph assumes a 72% active
time (device operating at the specified frequency) which is
typical in a monitor application. The other 28% of the time
the device is assumed to be sitting at the black level (75V in
this case). This graph gives the designer the information
needed to determine the heat sink requirement for his appli-
cation. The designer should note that if the load capacitance
is increased the AC component of the total power dissipation
will also increase.
The LM2471 case temperature must be maintained below
100C. If the maximum expected ambient temperature is
70C and the maximum power dissipation is 8.45W (from
Figure 6
, 160 MHz bandwidth) then a maximum heat sink
thermal resistance can be calculated:
This example assumes a capacitive load of 8 pF and no
resistive load.
TYPICAL APPLICATION
A typical application of the LM2471 is shown in
Figure 11
.
Used in conjunction with an LM1262, a complete video
channel from monitor input to CRT cathode can be achieved.
Performance is ideal for 1600 x 1200 resolution displays with
pixel clock frequencies up to 180 MHz. Please see the next
two sections below for hints on how to properly evaluate the
LM126X and LM2471 combination in a monitor.
Figure 10
shows the typical cathode response for this application. The
peaking component values used are shown in
Figure 11
.
PC BOARD LAYOUT CONSIDERATIONS
For optimum performance, an adequate ground plane, iso-
lation between channels, good supply bypassing and mini-
mizing unwanted feedback are necessary.Also, the length of
the signal traces from the preamplifier to the LM2471 and
from the LM2471 to the CRT cathode should be as short as
possible. The following references are recommended:
Ott, Henry W., “Noise Reduction Techniques in Electronic
Systems”, John Wiley & Sons, New York, 1976.
“Video Amplifier Design for Computer Monitors”, National
Semiconductor Application Note 1013.
Pease,
Robert
A.,
“Troubleshooting
Butterworth-Heinemann, 1991.
Because of its high small signal bandwidth, the part may
oscillate in a monitor if feedback occurs around the video
channel through the chassis wiring. To prevent this, leads to
the video amplifier input circuit should be shielded, and input
circuit wiring should be spaced as far as possible from output
circuit wiring.
Analog
Circuits”,
20103710
FIGURE 9. One Channel of the LM2471 with the
Recommended Application Circuit
20103716
40V
P-P
(35V–75V)
FIGURE 10. Typical Cathode Response
L
www.national.com
6
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM2471TA | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Monolithic Triple 4 ns High Swing CRT Driver |
| LM2476 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Monolithic Triple Channel 6.5 ns High Gain CRT Driver and Bias Clamp |
| LM2476TB | 功能描述:顯示驅(qū)動器和控制器 RoHS:否 制造商:Panasonic Electronic Components 工作電源電壓:2.7 V to 5.5 V 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-44 封裝:Reel |
| LM2476TB/NOPB | 功能描述:顯示驅(qū)動器和控制器 RoHS:否 制造商:Panasonic Electronic Components 工作電源電壓:2.7 V to 5.5 V 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-44 封裝:Reel |
| LM2479 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:120V Triple Bias Clamp |
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