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ADD8707 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer ADD8707
Beschreibung 12-Channel Gamma Buffers with VCOM and Regulator
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 20 Seiten
ADD8707 Datasheet, Funktion
FEATURES
12 precision gamma reference outputs
Mask-programmable gamma resistors:
0.2% resolution and 0.1% accuracy
Mask programmable voltage regulator: 0.4% accuracy
Upper 6 buffers swing to VDD
Lower 6 buffers swing to GND
Single-supply operation: 7.5 V to 16 V
Gamma current drive: 15 mA per channel
VCOM peak output current: 250 mA
Outputs stable under load conditions
48-lead, Pb-free LFCSP package
APPLICATIONS
LCD TV panels
LCD monitor panels
PRODUCT OVERVIEW
The ADD8707 is a 12-channel integrated gamma reference with
VCOM for use in LCD TV and monitor panels. The output
buffers feature high current drive and low offset voltage to
provide an accurate and stable gamma curve. The top six
channels swing to VDD and the lower six channels swing to
GND.
Integrating the gamma setup resistors drastically reduces the
external component count while increasing the gamma curve
accuracy. To accommodate multiple column drivers and panel
architectures, the ADD8707 is mask-programmable to a 0.2%
resolution using the on-chip 500 resistor string. An on-board
voltage regulator provides a fixed input for the resistor string,
isolating the gamma curve from supply ripple.
The ADD8707 is specified over the temperature range of
–40°C to +105°C and comes in a 48-lead, Pb-free, lead frame
chip-scale package.
12-Channel Gamma Buffers
with VCOM and Regulator
ADD8707
FUNCTIONAL BLOCK DIAGRAM
MASK-PROGRAMMABLE
REGULATOR RESISTORS
FB
700*
GND
+
1.2V
VIN11
VIN10
VIN8
VIN7
VIN6
VIN5
700*
700*
MASK-
PROGRAMMABLE
GAMMA RESISTORS
700*
700*
700*
700*
VIN3
VIN2
VIN1
700*
700*
700*
VCOM
GAMMA
BUFFERS
VCOM OUT
VOUT12
VOUT11
VOUT10
VOUT9
VOUT8
VOUT7
VOUT6
VOUT5
VOUT4
VOUT3
VOUT2
VOUT1
*ESD PROTECTION RESISTORS
Figure 1. 48-Lead LFCSP
Rev. A
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.
Specifications subject to change without notice. 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 owners.
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 © 2004 Analog Devices, Inc. All rights reserved.






ADD8707 Datasheet, Funktion
ADD8707
PIN CONFIGURATION AND FUNCTION DESCRIPTION
48 47 46 45 44 43 42 41 40 39 38 37
NC 1
GND 2
VDD 3
VREG OUT 4
FB 5
NC 6
NC 7
VIN11 8
VIN10 9
NC 10
VIN8 11
NC 12
ADD8707
TOP VIEW
(Not to Scale)
36 NC
35 NC
34 NC
33 VOUT4
32 VOUT3
31 VOUT2
30 VOUT1
29 VDD
28 GND
27 VCOM OUT
26 NC
25 NC
13 14 15 16 17 18 19 20 21 22 23 24
Figure 2. 48-Lead LFCSP
Table 4. Pin Function Descriptions
Pin No. Name
Description
1 NC
2 GND Ground. Normally 0 V.
3 VDD
Supply voltage. Normally 16 V.
4
VREG OUT
Regulator output voltage. Provides reference voltage to resistor string and is internally connected to the top of
the resistor string.
5 FB
Regulator feedback pin. Compares a percentage of the regulator output to the internal 1.2V voltage reference.
Internal resistors are used to program the desired regulator output voltage.
6 NC
7 NC
8
VIN11
Buffer inputs. Normally floating.1
9 VIN10
10 NC
11 VIN8
Buffer inputs. Normally floating.1
12 NC
13 NC
14 VIN7
15 VIN6
Buffer inputs. Normally floating.1
16 VIN5
17 NC
18 VIN3
19 VIN2
Buffer inputs. Normally floating.1
20 VIN1
21
VCOM IN-
VCOM amplifier inverting input.
22
VCOM IN+
VCOM amplifier non-inverting input.
23 NC
24 NC
1 External resistors can be added to modify the internal resistor string to change the gamma voltage. An external resistor calculator is available upon request.
Rev. A | Page 6 of 20

6 Page









ADD8707 pdf, datenblatt
ADD8707
APPLICATION NOTES
The ADD8707 is a mask-programmable gamma reference
generator that allows source drivers to be optimized for the
different combinations of liquid crystals, glass sizes, etc. in
large LCD panels. It generates 12 gamma reference outputs
that can be mask-programmed in 0.2% increments using the
500 matched internal resistors (Figure 23), so that every point
on the curve can be targeted within 0.1% of the desired value.
TAP POINT 4
TAP POINT 500
TAP POINT 3
TAP POINT 499
TAP POINT 2
TAP POINT 498
TAP POINT 1
TAP POINT 497
EACH R = 30
TYPICALLY
Figure 23. 500 Mask-Programmable Resistor String
In a typical panel application, the selected source drivers have
an internal gamma curve that is not ideal for the specific panel
(Figure 24). The ADD8707 allows the gamma curve in the
source drivers to be adjusted appropriately, and also insures that
all the source drivers have the same gamma curve.
16
14
12
10
8
ORIGINAL GAMMA CURVE
IN SOURCE DRIVERS
6
PANEL GAMMA CURVE
CORRECTED BY ADD8707
4
2
0
GAMMA REFERENCE INPUT POINTS
Figure 24. Original and Corrected Gamma Curves
The matching and tracking accuracy of the internal resistors is
typically 0.1% with worst-case deviation from the desired curve
within 0.4% of the ideal gamma curve, over temperature.
The ADD8707 also includes a low dropout linear regulator to
provide a stable reference level for the gamma curve for
optimum panel performance.
TAP POINT SELECTION
The ADD8707 uses a single resistor string consisting of 500
individual elements. The tap points are mask programmable
and completely independent of each other. Refer to the Tap
Point and Regulator Voltage Request Form in this data sheet.
VREG OUT
500–TPX
VINX
TPX
VOUTX
Figure 25. Gamma Buffers Tap Point Circuit.
Tap point voltages can be derived from the following equation:
VOUT
X
=
TPX
500
× VREG
OUT
where TPX is the desired tap point for the Xth channel.
Table 5. Typical Mask Implementation
VDD = 16 V, VREG OUT = 14.4 V, 0 ≤ X ≤ 500
Tap Point (X) Voltage
VOUT12
500
14.400
VOUT11
419
12.067
VOUT10
365
10.512
VOUT9
349
10.051
VOUT8
343
9.878
VOUT7
297
8.554
VOUT6
213
6.134
VOUT5
173
4.982
VOUT4
163
4.694
VOUT3
146
4.205
VOUT2
95
2.736
VOUT1
7
0.202
Units
V
V
V
V
V
V
V
V
V
V
V
V
Rev. A | Page 12 of 20

12 Page





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