12-Channel Gamma Buffers
with V
COM
Buffer
ADD8702
FEATURES
Programmable 12-Channel Gamma Reference Generator
Mask Programmable Adjustable V
COM
Buffer
Upper/Lower Outputs Swing to V
DD
/GND
Continuous Output Current: 10 mA
V
COM
Peak Output Current: 250 mA
Outputs with Fast Settling Time for Load Change
Output Pins Are Compatible with ADD8701
Single-Supply Operation: 7 V to 16 V
Supply Current: 15 mA Max
APPLICATIONS
TFT LCD Panels
FUNCTIONAL BLOCK DIAGRAM
V
COM
OUT
VGMA12
VGMA11
VGMA10
VGMA9
VGMA8
26
32
31
30
26
28
27
25
24
GND
23
V
DD
22
VGMA6
21
VGMA5
20
VGMA4
19
VGMA3
18
VGMA2
17
VGMA1
V
DD
V
COM
ADJ
V
HIGH
V
IN
11
V
IN
10
V
IN
9
V
IN
8
V
IN
7
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
V
LOW
V
IN
6
V
IN
5
V
IN
4
V
IN
3
V
IN
2
V
DD
The ADD8702 is a low cost, mask programmable, 12-channel
gamma reference generator, plus an adjustable V
COM
driver. This
part is designed to provide gamma correction for high resolution
TFT LCD panels. The 12 gamma reference levels and V
COM
are
mask programmable to 0.3% resolution using the on-chip 500
chain resistor string. This reduces component and board costs.
The ADD8702 provides a complete programmed set of gamma
voltage references for the LCD source drivers. These references
settle quickly to load change. The V
COM
output is stable with
high capacitive loads and can source or sink 250 mA peak cur-
rent. The V
COM
output level can be adjusted using an external
trim-potentiometer or discrete resistors.
The output pins are compatible with the ADD8701. This allows
for single board design and fast turns for prototyping using the
initial ADD8701 board design.
The ADD8702 is specified over the temperature range of –40°C
to +85°C and comes in the 32-lead lead frame chip scale pack-
age (LFCSP) for compact board space.
PANEL
TIMING
CONTROLLER
ADD8702
TIMING AND CONTROL
GAMMA
REFERENCE
VOLTAGES
GAMMA
V
COM
SCAN DRIVER CONTROL
SOURCE DRIVER
NO. 1
384
SOURCE DRIVER
NO. 2
384
SOURCE DRIVER
NO. 8
384
R G B
SCAN
DRIVERS
768
TFT COLOR PANEL
1024 768
Figure 1. Typical SVGA TFT LCD Application
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective companies.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
© 2003 Analog Devices, Inc. All rights reserved.
GND
GENERAL DESCRIPTION
VGMA7
GND
ADD8702–SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
(V
Parameter
OUTPUT ACCURACY
V
SYSTEM
ERROR
MASK PROGRAMMABLE
RESISTOR STRING
Total Resistor String
Resistor Matching
OUTPUT CHARACTERISTICS
Output Voltage High
(VGMA11, VGMA12)
Output Voltage Mid
(VGMA3 to VGMA10)
Output Voltage Low
(VGMA1, VGMA2)
Continuous Output Current
Peak Output Current
Settling Time—Voltage
V
COM
CHARACTERISTICS
Continuous Output Current
Peak Output Current
Settling Time—Voltage
SUPPLY CHARACTERISTICS
Supply Voltage
Power Supply Rejection Ratio
SUPPLY CURRENT
Symbol
V
SY ERROR
DD
= 16 V, T
A
= 25 C, unless otherwise specified.)
Min
Typ
10
Max
50
Unit
mV
Conditions
R
TOTAL
R
MATCH
V
OUT
V
OUT
V
OUT
I
OUT
I
PK
t
S
I
OUT
I
PK
t
S
V
DD
PSRR
I
SYS
500 Elements V
LOW
to V
HIGH
Any Two Segments
I
L
= 100
µA
I
L
= 5 mA
–40°C
≤
T
A
≤
+85°C
I
L
= 5 mA
I
L
= 100
µA
I
L
= 5 mA
–40°C
≤
T
A
≤
+85°C
1 V Step 0.1%, R
L
= 10 kΩ, C
L
= 200 pF
22.5
1
15.995
15.95
14.6
5
50
10
150
1
35
250
0.8
7
68
16
75
11
15
16
kΩ
%
V
V
V
V
mV
mV
mV
mA
mA
µs
mA
mA
µs
V
dB
mA
mA
15.85
15.75
150
250
1 V Step 0.1%, R
L
= 10 kΩ, C
L
= 200 pF
V
S
= 6 V to 17 V, –40°C
≤
T
A
≤
+85°C
No Load
–40°C
≤
T
A
≤
+85°C
Specifications subject to change without notice.
–2–
REV. 0
ADD8702
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage (V
S
) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 V
Storage Temperature Range . . . . . . . . . . . . . –65°C to +150°C
Operating Temperature Range . . . . . . . . . . . . –40°C to +85°C
Junction Temperature Range . . . . . . . . . . . . . –65°C to +150°C
Lead Temperature Range (Soldering, 60 sec.) . . . . . . . . 300°C
ESD Tolerance (HBM) . . . . . . . . . . . . . . . . . . . . . . .
±
1,000 V
*Stresses
above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those indicated in the operational
sections of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.
Package Type
32-Lead LFCSP (CP)
JA
1
2
JB
Unit
°C/W
35
13
NOTES
1
θ
JA
is specified for worst-case conditions, i.e.,
θ
JA
is specified for device soldered
in circuit board for surface-mount packages.
2
ψ
JB
is applied for calculating the junction temperature by reference to the board
temperature.
ORDERING GUIDE
Model
ADD8702ACP-R2
ADD8702ACP-REEL
ADD8702ACP-REEL7
Temperature
Range
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
Package
Description
32-Lead LFCSP
32-Lead LFCSP
32-Lead LFCSP
Package
Option
CP-32
CP-32
CP-32
PIN CONFIGURATION
32 V
COM
OUT
31 GND
30 VGMA12
29 VGMA11
28 VGMA10
27 VGMA9
26 VGMA8
25 VGMA7
V
DD
1
V
COM
ADJ 2
V
HIGH
3
V
IN
11 4
V
IN
10 5
V
IN
9 6
V
IN
8 7
V
IN
7 8
PIN 1
INDICATOR
ADD8702
TOP VIEW
24 GND
23 V
DD
22 VGMA6
21 VGMA5
20 VGMA4
19 VGMA3
18 VGMA2
17 VGMA1
PIN FUNCTION DESCRIPTIONS
Pin No.
1, 15, 23
2
3
4–13
14
16, 24, 31
17–22, 25–30
32
Mnemonic
V
DD
V
COM
ADJ
V
HIGH
V
IN
11–V
IN
2
V
LOW
GND
VGMA1–VGMA12
V
COM
OUT
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection. Although the
ADD8702 features proprietary ESD protection circuitry, permanent damage may occur on devices
subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended
to avoid performance degradation or loss of functionality.
REV. 0
V
IN
6 9
V
IN
5 10
V
IN
4 11
V
IN
3 12
V
IN
2 13
V
LOW
14
V
DD
15
GND 16
Description
Power (+)
V
COM
Adjust Input
Highest Gamma Input Voltage
Gamma Buffer Inputs
Lowest Gamma Input Voltage
Power (–)
Gamma Buffer Outputs
V
COM
Buffer Output
–3–
ADD8702–Typical Performance Characteristics
12
T
A
= 25 C
10
12
V
DD
= 16V
11
SUPPLY CURRENT (mA)
10
V
DD
= 16V
GAMMA 1 TO 9
0
2k , 10k
SUPPLY CURRENT (mA)
10
9
8
7
–30
8
GAIN (dB)
–10
150
–20
6
4
2
6
5
–40
–40
100k
0
0
4
8
12
SUPPLY VOLTAGE (V)
16
25
TEMPERATURE ( C)
85
1M
10M
FREQUENCY (Hz)
30M
TPC 1. Supply Current vs.
Supply Voltage
TPC 2. Supply Current vs.
Temperature
TPC 3. Frequency Response
vs. Resistive Loading
10
V
DD
= 16V
GAMMA 10 TO 12
0
2k , 10k
10
V
DD
= 16V
V
COM
2k , 10k
–10
20
V
DD
= 16V
GAMMA 1 TO 9
10
50pF
150
0
GAIN (dB)
GAIN (dB)
GAIN (dB)
–10
150
–20
0
340pF
–10
540pF
100pF
–20
–30
–30
–40
–20
1040pF
–40
100k
1M
10M
FREQUENCY (Hz)
30M
–50
100k
1M
10M
FREQUENCY (Hz)
30M
–30
100k
1M
10M
FREQUENCY (Hz)
30M
TPC 4. Frequency Response
vs. Resistive Loading
TPC 5. Frequency Response
vs. Resistive Loading
TPC 6. Frequency Response
vs. Capacitive Loading
20
V
DD
= 16V
GAMMA 10 TO 12
10
20
V
DD
= 16V
V
COM
180
160
PHASE SHIFT (Degrees)
10
V
DD
= 16V
GAMMA 1 TO 12
R
L
= 2k
GAMMA 12
GAMMA 1
140
120
100
80
60
40
GAIN (dB)
340pF
–10
540pF
–20
1040pF
–30
100k
100pF
GAIN (dB)
0
50pF
0
–10
340pF
100pF
–20
540pF
1040pF
50pF
30M
1M
10M
FREQUENCY (Hz)
30M
–30
100k
1M
10M
FREQUENCY (Hz)
0
200
400
600
800 1,000
CAPACITIVE LOAD (pF)
1,200
TPC 7. Frequency Response
vs. Capacitive Loading
TPC 8. Frequency Response
vs. Capacitive Loading
TPC 9. Input and Output Phase
Shift vs. Capacitive Load
–4–
REV. 0
ADD8702
16
V
DD
= 16V
R
L
= 10k
C
L
= 100pF
14
12
V
DD
= 16V
R
NULL
= 33
C
L
= 100pF
10
V
COM
SLEW RATE FALLING
8
V
COM
SLEW RATE RISING
6
4
2
0
–40
VOLTAGE (20mV/DIV)
SLEW RATE (V/ s)
VOLTAGE (2V/DIV)
7V < V
DD
< 16V
R
NULL
= 33
C
L
= 0.1 F
25
TEMPERATURE ( C)
85
TIME (2 s/DIV)
TIME (20 s/DIV)
TPC 10. Large Signal Transient
Response
TPC 11. Slew Rate vs. Temperature
TPC 12. Small Signal Transient
Response
11
10
9
8
V
DD
= 16V
GAMMA = 2
11
10
9
V
DD
= 16V
GAMMA = 11
11
10
9
V
DD
= 16V
V
COM
AMPLITUDE (V)
7
6
5
4
3
2
1
0
–200
AMPLITUDE (V)
AMPLITUDE (V)
120pF
320pF
1 F 10 F
8
7
6
5
4
3
2
1
320pF
120pF
1 F 10 F
8
7
6
5
4
3
2
1
120pF
320pF
1 F 10 F
520pF
520pF
520pF
200
600
1,000
TIME (ns)
1,400
1,800
0
–200
200
600
1,000
TIME (ns)
1,400
1,800
0
–200
200
600
1,000
TIME (ns)
1,400
1,800
TPC 13. Transient Load
Response vs. Capacitive Load
TPC 14. Transient Load
Response vs. Capacitive Load
TPC 15. Transient Load
Response vs. Capacitive Load
100
OUTPUT VOLTAGE ERROR (mV)
OUTPUT VOLTAGE ERROR (mV)
80
70
60
50
SINK
40
30
20
10
0
0.001
0.01
0.1
1
10
LOAD CURRENT (mA)
100
SOURCE
OUTPUT VOLTAGE ERROR (mV)
V
DD
= 16V
90 GAMMA 1 TO 9
1,400
1,200
1,000
800
600
400
200
V
DD
= 16V
GAMMA 10 TO 12
SINK
50
V
DD
= 16V
45 V
COM
40
35
30
25
20
SOURCE
15
10
SINK
5
0
0.001
SOURCE
0
0.001
0.01
0.1
1
10
LOAD CURRENT (mA)
100
0.01
0.1
1
10
LOAD CURRENT (mA)
100
TPC 16. Output Voltage
Error vs. Load Current
TPC 17. Output Voltage
Error vs. Load Current
TPC 18. Output Voltage
Error vs. Load Current
REV. 0
–5–
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