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參數(shù)資料
| 型號： | LM8207 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | TFT 18 Gamma Buffer + VCOM Driver + Voltage Reference |
| 中文描述： | 液晶18伽瑪緩沖器的VCOM驅動電壓基準 |
| 文件頁數(shù)： | 17/22頁 |
| 文件大?。?/td> | 1393K |
| 代理商： | LM8207 |
Application Section
(Continued)
V
COM
BUFFER
The V
COM
buffer supplies a common voltage to the back
plate of all the pixels in a TFT panel. When column drivers
write to the pixels, current pulses will occur onto the V
COM
line. These pulses are the result of charging the capacitance
between V
and the column lines. This capacitance is a
combination of stray capacitance and pixel capacitance. This
stray capacitance varies between panel sizes but typically
ranges from 16 pF to 33 pF per column. Pixel capacitance is
in the order of 0.5 pF and contributes very little to these
pulses because only one pixel at a time is connected to a
column. Charging this capacitance can result in short posi-
tive or negative current pulses of 100 mA or more, depend-
ing on the panel size. The V
buffer is designed to handle
these pulses. A V
buffer is basically a voltage regulator
that can sink or source current in large capacitive loads. The
V
buffer should recover very fast from these distur-
bances. The operating voltage of the V
COM
buffer is in the
middle of the gamma voltage range.
The typical application in
Figure 11
shows the V
COM
buffer
supplying a common voltage to the back plate of the display.
This level can be adjusted by changing the value of the
resistors. Increasing the value of R
1
or decreasing the value
of R
2
will decrease the V
COM
level. Increasing the value of
R
2
or decreasing the value of R
1
will increase the V
COM
level.
Another, more flexible, solution is to use National Semicon-
ductor’s programmable V
COM
calibrator, the LM8342. The
V
level can be adjusted using an I
2
C interface. See the
LM8342’s datasheet for more detailed information about this
part.
LM8207 CONFIGURATION
A complete configured typical application of the LM8207 is
given in
Figure 12
. All three basic functions of the LM8207
are discussed in the previous sections. Details for setting the
Voltage Reference are given in the “Voltage Reference”
section. Calculations for defining a gamma correction curve
are given in the section entitled “Gamma Buffers.” Defining
and adjusting the V
level is discussed in the “V
Buffer” section. The LM8207 is an 18 channel gamma buffer
plus a V
buffer. In certain applications some of the
gamma buffers or the V
buffer may not be used. In such
cases it is recommended that the unused buffer input pins be
tied to the input voltage range value.
20137928
FIGURE 11. VCOM Buffer
L
www.national.com
17
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LM8207MT | 功能描述:LCD 驅動器 RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率:19 KHz 工作電源電壓:3 V to 3.6 V 最大工作溫度:+ 85 C 最小工作溫度:- 20 C 封裝 / 箱體:PDIP-40 封裝:Tube |
| LM8207MT/NOPB | 功能描述:LCD Gamma緩沖器 RoHS:否 制造商:Maxim Integrated 輸入補償電壓: 轉換速度: 電源電壓-最大:20 V 電源電壓-最小:9 V 電源電流: 最大功率耗散: 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:TQFN-38 封裝:Tube |
| LM8207MTX | 功能描述:LCD 驅動器 RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率:19 KHz 工作電源電壓:3 V to 3.6 V 最大工作溫度:+ 85 C 最小工作溫度:- 20 C 封裝 / 箱體:PDIP-40 封裝:Tube |
| LM8207MTX/NOPB | 功能描述:LCD 驅動器 RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率:19 KHz 工作電源電壓:3 V to 3.6 V 最大工作溫度:+ 85 C 最小工作溫度:- 20 C 封裝 / 箱體:PDIP-40 封裝:Tube |
| LM825 | 制造商:Pulse Electronics Corporation 功能描述: |
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