BUF16820 Datasheet, PDF (17/30 Pages) Burr-Brown (TI) – 14-Channel GAMMA VOLTAGE GENERATOR with Programmable VCOM Outputs and OTP Memory

BUF16820
www.ti.com
CONFIGURATION FOR 16 GAMMA CHANNELS
The V_COM outputs can be used as additional gamma
references in order to achieve two additional gamma
channels (16 total). The V_COM outputs will behave the
same as the OUT1−9 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, as
shown in Figure 16.
CONFIGURATION FOR 18 GAMMA CHANNELS
In addition to the V_COM outputs, the REFH and REFL OUT
outputs can also be used as fixed gamma references. The
output voltage is set by the REFH and REFL input
SBOS356A − FEBRUARY 2006 − REVISED OCTOBER 2006
voltages, respectively. Therefore, REFH OUT should be
used for the highest voltage gamma reference, and REFL
OUT for the lowest voltage gamma reference. An
18-channel solution can be created by using all 14 outputs,
the two V_COM outputs, and both REFH/L OUT outputs for
gamma references; see Figure 17. However, the REFH
and REFL OUT buffers were designed to only drive light
loads on the order of 5mA to 10mA. Driving capacitive
loads is not recommended with these buffers. In addition,
the REFH and REFL buffers must not be allowed to
saturate from sourcing/sinking too much current from
REFH OUT or REFL OUT. Saturation of the REFH and
REFL buffers results in errors in the voltages of OUT1−14,
V_COM1, and V_COM2. The BUF01900 (anticipated release in
Q2 ‘06), can be used to provide a programmable V_COM
output.
BUF16820
18V
2V to 5.5V
Digital
Analog
17.8V
REFH
REFH OUT
17V
Source
Driver
V_{COM 1}
GMA 1
V_{COM 2}
GMA 2
OUT1
OUT2
GMA 3
GMA 4
2 V_COM Channels plus
14 Gamma Channels
OUT13
GMA 15
SDA
SCL
Control IF
OUT14
REFL OUT
0.2V
GMA 16
LD
A0
REFL
18V
0.2V
Figure 16. 16 Gamma Channel Solution—2 V_COM Channels Used as Additional Gamma Channels
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