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參數資料
| 型號： | LM2476 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Monolithic Triple Channel 6.5 ns High Gain CRT Driver and Bias Clamp |
| 中文描述： | 單片6.5納秒三通道CRT顯示器驅動高增益和偏置夾 |
| 文件頁數： | 7/12頁 |
| 文件大小： | 1235K |
| 代理商： | LM2476 |
Application Hints
(Continued)
OPTIMIZING TRANSIENT RESPONSE
Referring to
Figure 12
, 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 14
can be used as a good starting
point for the evaluation of the LM2476. 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 OFFSET
Figure 8
shows the variation in rise and fall times when the
output offset of the device is varied from 50 to 60VDC. The
rise time shows a maximum variation of 13% relative to the
center data point (55 V
). The fall time shows a maximum
variation of less than 3% relative to the center data point.
EFFECT OF LOAD CAPACITANCE
Figure 9
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.
THERMAL CONSIDERATIONS
Figure 10
shows the performance of the LM2476 in the test
circuit shown in
Figure 4
as a function of case temperature
(on the device tab). The figure shows that the rise and fall
times of the LM2476 increase by approximately 10% and
5%, respectively, as the case temperature increases from
50C to 100C. This corresponds to a speed degradation of
2% and 1%, respectively, for every 10C rise in case tem-
perature.
Figure 11
shows the maximum power dissipation of the
LM2476 vs. Frequency when all three channels of the device
are driving an 8 pF load with a 40 V
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 LM2476 case temperature must be maintained below
100C. If the maximum expected ambient temperature is
70C and the maximum power dissipation is about 6W (from
Figure 11
, 95 MHz bandwidth), then a maximum heat sink
thermal resistance can be calculated:
PACKAGE MOUNTING CONSIDERATIONS
Mounting of the TO-247 package to a heat sink must be
done such that there is sufficient pressure from the mounting
screws to insure good contact with the heat sink for efficient
heat flow. The surface of the heat sink should be free of
contaminants before mounting to insure good contact. Incor-
rect mounting may lead to both thermal and mechanical
problems. Over tightening the mounting screws will cause
the package to warp, reducing contact area with the heat
sink. Less contact with the heat sink will increase the thermal
resistance from the package case to the heat sink (
θ
)
resulting in higher operating die temperatures. Extreme over
tightening of the mounting screws will cause severe physical
stress resulting in a cracked or chipped package and pos-
sible catastrophic IC failure.
The recommended mounting screw size is M3 with a maxi-
mum torque of 50 N-cm. It is best to use fiber washers under
the screws to distribute the force over a wider area. Addi-
tionally, if the mounting screws are used to force the pack-
age into correct alignment with the heat sink, package stress
20121910
FIGURE 12. One Channel of the LM2476 with the Recommended Application Circuit
L
www.national.com
7
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LM2476TB | 功能描述:顯示驅動器和控制器 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: 安裝風格:SMD/SMT 封裝 / 箱體:QFN-44 封裝:Reel |
| LM2476TB/NOPB | 功能描述:顯示驅動器和控制器 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 |
| LM2479BN WAF | 制造商:Texas Instruments 功能描述: |
| LM2479NA | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:120V Triple Bias Clamp |
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