BUF11705 Datasheet, PDF (10/17 Pages) Burr-Brown (TI) – 22 - V Supply, 10 + 1 Channel Gamma Correction Buffer

BUF11705
SBOS349 − DECEMBER 2005
ESD RATINGS
The BUF11705 has excellent ESD performance: 8 kV
HBM; 2 kV CDM; and 300 V MM. These ESD ratings
allow for increased manufacturability, fewer production
failures, and higher reliability.
INPUT VOLTAGE RANGE GAMMA BUFFERS
Figure 22 shows a typical gamma correction curve with
10 gamma correction reference points (GMA1 through
GMA10). As can be seen from this curve, the voltage
requirements for each buffer vary greatly. The swing
capability of the input stages of the various buffers is
carefully matched to the application. Buffers 1 through
5 have input stages that include V_DD, but will only swing
within 1 V to GND. Buffers 1 through 5 have only a single
NMOS input stage. Buffers 6 through 10 have only a
single PMOS input stage. The input range of the PMOS
input stage includes GND.
V_DD1
GMA1
GMA2
GMA3
GMA4
GMA5
GMA6
GMA7
GMA8
GMA9
GMA10
V_SS1
0
10
20
30
40
Input Data (Hex)
Figure 22. Gamma Correction Curve
OUTPUT VOLTAGE SWING GAMMA BUFFERS
The output stages have been designed to match the
characteristic of the input stage. This means that the
output stage of buffers 1 through 5 swing very close to
www.ti.com
V_DD (typically, V_CC − 100 mV at 10 mA). The ability of
buffers 1 through 5 to swing to GND is limited. Buffers
6 through 10 swing closer to GND than V_DD. Buffers 6
through 10 are designed to swing very close to GND;
typically, GND + 100 mV at a 10 mA load current. See
the Typical Characteristics for more details. This
approach significantly reduces the silicon area and
overall cost of the whole solution. However, due to this
architecture, the correct buffer must be connected to
the correct gamma correction voltage. Connect buffer
1 to the gamma voltage closest to V_DD, and buffers 2
through 5 to the sequentially voltages. Buffer 10 should
be connected to the gamma correction voltage closest
to GND (or the negative rail), and buffers 9 through 6 to
the sequentially higher voltages.
COMMON BUFFER (V_COM)
The common buffer output of the BUF11705 has a
greater output drive capability than the gamma buffers
in order to meet the heavier current demands of driving
the common node of the LCD panel. The common
buffer output was also designed to drive heavier
capacitive loads. Excellent output swing is possible with
high currents ( > 100 mA), as shown in Figure 23.
OUTPUT VOLTAGE vs OUTPUT CURRENT
18
17
16
15
14
13 VDD = 18 V
12 T_A = 25_ C
11
7
6
5
4
3
2
1
0
0 25 50 75 100 125 150 175 200 225 250
Output Current − mA
Figure 23. V_COM Output Drive Capability
10