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參數(shù)資料
| 型號： | LM6584 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | TFT-LCD Quad, 13V RRIO High Output Current |
| 中文描述： | TFT - LCD的四路，13V的RRIO高輸出電流 |
| 文件頁數(shù)： | 11/16頁 |
| 文件大?。?/td> | 976K |
| 代理商： | LM6584 |
TFT Display Application
(Continued)
light filter that modulates light transmitted from the back to
the front of a display. A pixel’s bottom plate lies on the
backside of a display where a light source is applied, and the
top plate lies on the front, facing the viewer. On a Twisted
Neumatic (TN) display, which is typical of most TFT displays,
a pixel transmits the greatest amount of light when V
is
less
±
0.5V, and it becomes less transparent as this voltage
increases with either a positive or negative polarity. In short,
an LCD pixel can be thought of as a capacitor, through
which, a controlled amount of light is transmitted by varying
V
PIXEL
.
Figure 2
is a simplified block diagram of a TFT display,
showing how individual pixels are connected to the row,
column, and V
lines. Each pixel is represented by ca-
pacitor with an NMOS transistor connected to its top plate.
Pixels in a TFT panel are arranged in rows and columns.
Row lines are connected to the NMOS gates, and column
lines to the NMOS sources. The back plate of every pixel is
connected to a common voltage called V
COM
. Pixel bright-
ness is controlled by voltage applied to the top plates, and
the Column Drivers supply this voltage via the column lines.
Column Drivers ‘write’ this voltage to the pixels one row at a
time, and this is accomplished by having the Row Drivers
select an individual row of pixels when their voltage levels
are transmitted by the Column Drivers. The Row Drivers
sequentially apply a large positive pulse (typically 25V to
35V) to each row line. This turns-on NMOS transistors con-
nected to an individual row, allowing voltages from the col-
umn lines to be transmitted to the pixels.
V
COM
DRIVER
The V
COM
driver supplies a common voltage (V
COM
) to all
the pixels in a TFT panel. V
COM
is a constant DC voltage that
lies in the middle of the column drivers’ output voltage range.
As a result, when the column drivers write to a row of pixels,
they apply voltages that are either positive or negative with
respect to V
. In fact, the polarity of a pixel is reversed
each time its row is selected. This allows the column drivers
to apply an alternating voltage to the pixels rather than a DC
signal, which can ‘burn’ a pattern into an LCD display.
When column drivers write to the pixels, current pulses are
injected onto the V
line. These pulses result from charg-
ing stray capacitance between V
and the column lines
(see
Figure 2
), which ranges typically from 16pF to 33pF per
column. Pixel capacitance contributes very little to these
pulses because only one pixel at a time is connected to a
column, and the capacitance of a single pixel is on the order
of only 0.5pF. Each column line has a significant amount of
series resistance (typically 2k
to 40k
), so the stray ca-
pacitance is distributed along the entire length of a column.
This can be modeled by the multi-segment RC network
shown in
Figure 3
. The total capacitance between V
and
the column lines can range from 25nF to 100nF, and charg-
ing this capacitance can result in positive or negative current
pulses of 100mA, or more. In addition, a similar distributed
capacitance of approximately the same value exists be-
tween V
COM
and the row lines. Therefore, the V
COM
driver’s
load is the sum of these distributed RC networks with a total
capacitance of 50nF to 200nF, and this load can modeled
like the circuit in
Figure 3
.
A V
driver is essentially a voltage regulator that can
source and sink current into a large capacitive load. To
simplify the analysis of this driver, the distributed RC network
of
Figure 3
has been reduced to a single RC load in
Figure
4
. This load places a large capacitance on the V
driver
output, resulting in an additional pole in the op amp’s feed-
back loop. However, the op amp remains stable because
C
and R
create a zero that cancels the effect of this
pole. The range of C
is 50nF to 200nF and R
is 20
to 100
, so this zero will have a frequency in the range of
20059226
FIGURE 1. Individual LCD Pixel
20059227
FIGURE 2. TFT Display
20059228
FIGURE 3. Model of Impedance between V
COM
and
Column Lines
L
www.national.com
11
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相關(guān)代理商/技術(shù)參數(shù) |
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|---|---|
| LM6584MA | 功能描述:運算放大器 - 運放 RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LM6584MA/NOPB | 功能描述:運算放大器 - 運放 RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LM6584MAX | 功能描述:運算放大器 - 運放 RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LM6584MAX/NOPB | 功能描述:運算放大器 - 運放 RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LM6584MT | 功能描述:運算放大器 - 運放 RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
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