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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)： | 12/16頁 |
| 文件大?。?/td> | 976K |
| 代理商： | LM6584 |
TFT Display Application
(Continued)
8KHz to160KHz, which is much lower than the gain band-
width of most op amps. As a result, the V
COM
load adds very
little phase lag when op amp loop gain is unity, and this
allows the V
COM
Driver to remain stable. This was verified by
measuring the small-signal bandwidth of the LM6584 with
the RC load of
Figure 4
. When driving an RC load of 50nF
and 20
, the LM6584 has a unity gain frequency of 6.12MHz
with 41.5C of phase margin. If the load capacitor is in-
creased to 200nF and the resistance remains 20
, the unity
gain frequency is virtually unchanged: 6.05MHz with 42.9C
of phase margin.
A V
COM
Driver’s large-signal response time is determined by
the op amp’s maximum output current, not by its slew rate.
This is easily shown by calculating how much output current
is required to slew a 50nF load capacitance at the LM6584
slew rate of 14V/μs:
I
OUT
= 14V/μs x 50nF
= 700mA
700mA exceeds the maximum current specification for the
LM6584 and almost all other op amps, confirming that a
V
driver’s speed is limited by its peak output current. In
order to minimize V
transients, the op amp used as a
V
COM
Driver must supply large values of output current.
Figure 5
is a common test circuit used for measuring V
COM
driver response time. The RC network of R
L1
to R
L3
and C
1
to C
models the distributed RC load of a V
line. This RC
network is a gross simplification of what the actual imped-
ance is on a TFT panel. However, it does provide a useful
test for measuring the op amp’s transient response when
driving a large capacitive load. A low impedance MOSFET
driver applies a 5V square wave to V
, generating large
current pulses in the RC network. Scope photos from this
circuit are shown in
Figure 6
and
Figure 7
.
Figure 6
shows
the test circuit generates positive and negative voltage
spikes with an amplitude of
±
3.2V at the V
COM
node, and
both transients settle-out in approximately 2μs. As men-
tioned before, the speed at which these transients settle-out
is a function of the op amp’s peak output current. The I
OUT
trace in
Figure 7
shows that the LM6584 can sink and source
peak currents of 310mA and 320mA. This ability to supply
large values of output current makes the LM6584 extremely
well suited for V
COM
Driver applications.
GAMMA BUFFER
Illumination in a TFT display, also referred to as grayscale, is
set by a series of discrete voltage levels that are applied to
each LCD pixel. These voltage levels are generated by
resistive DAC networks that reside inside each of the column
driver ICs. For example, a column driver with 64 Grayscale
20059229
FIGURE 4. V
COM
Driver with Simplified Load
20059230
FIGURE 5. V
COM
Driver Test Circuit
20059231
FIGURE 6. V
SW
and V
COM
Waveforms from V
COM
20059232
FIGURE 7. V
SW
and I
OUT
Waveforms from V
COM
Test
Circuit
L
www.national.com
12
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM6584MA | 功能描述:運(yùn)算放大器 - 運(yùn)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(bǔ)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(yùn)算放大器 - 運(yùn)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(bǔ)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(yùn)算放大器 - 運(yùn)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(bǔ)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(yùn)算放大器 - 運(yùn)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(bǔ)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(yùn)算放大器 - 運(yùn)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(bǔ)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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