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參數(shù)資料
| 型號： | BUF20820AIDCPRE4 |
| 英文描述： | 18-Channel GAMMA VOLTAGE GENERATOR with Two Programmable VCOM Channels |
| 中文描述： | 18通道伽瑪雙通道可編程的VCOM電壓發(fā)生器 |
| 文件頁數(shù)： | 17/32頁 |
| 文件大小： | 1826K |
| 代理商： | BUF20820AIDCPRE4 |
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SBOS330C DECEMBER 2005 REVISED OCTOBER 2006
www.ti.com
17
PROGRAMMABLE V
COM
The V
COM
channels of the BUF20820 can swing to 2.5V
from the positive supply rail while sourcing 100mA, and to
1V above the negative rail while sinking 100mA (see
Figure 4, typical characteristic
Output Voltage vs Output
Current
). The gamma and the V
COM
values can be
permanently stored in the internal OTP memory. The V
COM
channels can be programmed independently from the
gamma channels. Figure 14 shows the BUF20820 being
used for V
COM
voltages.
BUF20820
SDA
SCL
R
Control Interface
Gamma
References
OUT1
OUT2
OUT17
OUT18
V
COM
V
COM OUT1
V
COM OUT2
Figure 14. BUF20820 Used for Programmable
V
COM
REFH AND REFL INPUT RANGE
Best performance and output swing range of the
BUF20820 are achieved by applying REFH and REFL
voltages that are slightly below the power-supply voltages.
Most
specifications
have
REFH = V
S
200mV and REFL = GND + 200mV. The
REFH internal buffer is designed to swing very closely to
been
tested
at
V
S
and the REFL internal buffer to GND. However, there
is a finite limit on how close they can swing before
saturating. To avoid saturation of the internal REFH and
REFL buffers, the REFH voltage should not be greater
than V
S
100mV and REFL voltage should not be lower
than GND + 100mV. Figure 15 shows the swing capability
of the REFH and REFL buffers.
The other consideration when trying to maximize the
output swing capability of the gamma buffers is the
limitation in the swing range of output buffers (OUT118,
V
COM
1, and V
COM
2), which depends on the load current. A
typical load in the LCD application is 510mA. For
example, if OUT1 is sourcing 10mA, the swing is typically
limited to about V
S
200mV. The same applies to OUT18,
which typically limits at GND + 200mV when sinking
10mA. An increase in output swing can only be achieved
for much lighter loads. For example, a 3mA load typically
allows the swing to be increased to approximately
V
S
100mV and GND + 100mV.
Connecting REFH directly to V
S
and REFL directly to GND
does not damage the BUF20820. As discussed above
however, the output stages of the REFH and REFL buffers
will saturate. This condition is not desirable and can result
in a small error in the measured output voltages of
OUT118, V
COM OUT1
, and V
COM OUT2
. As described above,
this method of connecting REFH and REFL does not help
to maximize the output swing capability.
18
17
16
15
3
2
1
0
O
0
10
20
100
40
50
60
70
80
90
30
Output Current (mA)
REFL OUT (sinking), Code = 000h
V
REFL
= 0.2V, V
REFH
= 17V
R
LOAD
Connected to 18V
REFH OUT (sourcing), Code = 3FFh
V
REFL
= 1V, V
REFH
= 17.8V
R
LOAD
Connected to GND
Figure 15. Reference Buffer Output Voltage vs
Output Current
CONFIGURATION FOR 20 GAMMA CHANNELS
The V
COM
outputs can be used as additional gamma
references in order to achieve two additional gamma
channels (20 total). The V
COM
outputs will behave the
same as the OUT19 outputs when sourcing or sinking
smaller currents (see the Typical Characteristics,
Figure 4). The V
COM
outputs are better able to swing to the
positive rail than to the negative rail. Therefore, it is better
to use the V
COM
outputs for higher reference voltages; see
Figure 16.
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| BUF20820EVM | 功能描述:放大器 IC 開發(fā)工具 BUF20800-BUF20820 Eval Mod RoHS:否 制造商:International Rectifier 產(chǎn)品:Demonstration Boards 類型:Power Amplifiers 工具用于評估:IR4302 工作電源電壓:13 V to 23 V |
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| BUF22821EVM | 功能描述:放大器 IC 開發(fā)工具 BUF22821EVM Eval Mod RoHS:否 制造商:International Rectifier 產(chǎn)品:Demonstration Boards 類型:Power Amplifiers 工具用于評估:IR4302 工作電源電壓:13 V to 23 V |
| BUF22821EVM-USB | 功能描述:放大器 IC 開發(fā)工具 BUF22821 Eval board Mod RoHS:否 制造商:International Rectifier 產(chǎn)品:Demonstration Boards 類型:Power Amplifiers 工具用于評估:IR4302 工作電源電壓:13 V to 23 V |
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