Analog Devices ADD8708 Datasheet

18-Channel Gamma Buffer

FEATURES

18 precision gamma reference outputs
Mask-programmable gamma resistors:

0.2% resolution and 0.1% accuracy
Mask-programmable voltage regulator: 0.4% accuracy
Upper 9 buffers swing to V
Lower 9 buffers swing to GND
Single-supply operation: 7.5 V to 16.5 V
Gamma current drive: 15 mA per channel
Peak output current: 150 mA
Output voltage stable under load conditions
Pin-to-pin compatible with ADD8709
48-lead, Pb-free LQFP and LFCSP

APPLICATIONS

LCD TV panels
LCD monitor panels

GENERAL DESCRIPTION

The ADD8708 is an 18-channel integrated gamma reference for
use in high resolution LCD TV and monitors panels. The out­put buffers feature high current drive and low offset voltage to
provide an accurate and stable gamma curve. The top nine
channels swing to V

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 ADD8708 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 the supply ripple.

The ADD8708 is specified over the temperature range of
–40°C to +105°C and comes in both a 48-lead, Pb-free,
lead-frame chip-scale package and a Pb-free, low-profile,
quad flat package.

DD

; the lower nine channels swing to GND.

DD

FUNCTIONAL BLOCK DIAGRAM

MASK-PROGRAMMABLE
REGULATOR RESISTORS

GND

1.2V

18

V

IN

V

17

IN

V

16

IN

V

15

IN

V

14

IN

V

13

IN

V

12

IN

V

11

IN

V

10

IN

V

IN

V

IN

V

IN

V

IN

V

IN

V

IN

V

IN

V

IN

V

IN

700Ω*

700Ω*

700Ω*

700Ω*

700Ω*

700Ω*

700Ω*

700Ω*

700Ω*

700Ω*

9

700Ω*

8

700Ω*

7

700Ω*

6

700Ω*

5

700Ω*

4

700Ω*

3

700Ω*

2

700Ω*

1

MASK-PROGRAMMABLE
RESISTOR STRING

*ESD PROTECTION RESISTORS

Figure 1. 48-Lead LQFP or LFCSP

FB V

700Ω*

+
–

with Regulator

ADD8708

VDDV

REG OUT

DD

GAMMA
BUFFERS

GND GND

V

18

OUT

V

17

OUT

V

16

OUT

V

15

OUT

V

14

OUT

V

13

OUT

V

12

OUT

V

11

OUT

V

10

OUT

V

9

OUT

V

8

OUT

V

7

OUT

V

6

OUT

V

5

OUT

V

4

OUT

V

3

OUT

V

2

OUT

V

1

OUT

04614-001

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.
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: [phone]
Fax: [phone] © 2004 Analog Devices, Inc. All rights reserved.

www.analog.com

ADD8708

TABLE OF CONTENTS

Electrical Characteristics................................................................. 3

Absolute Maximum Ratings............................................................ 4

ESD Caution.................................................................................. 4

Pin Configuration and Function Descriptions............................. 5

Typical Performance Characteristics ............................................. 7

Application Notes ........................................................................... 10

Tap Point Selection..................................................................... 10

Volt a ge R e gu l ator ....................................................................... 11

Maximum Power Dissipation ...................................................11

Land Pattern................................................................................ 11

Operating Temperature Range ................................................. 12

Typical Applications Ci r c u it ..........................................................14

Tap Point and Regulator Voltage Request Form......................... 15

Outline Dimensions ....................................................................... 16

Ordering Guide........................................................................... 16

REVISION HISTORY

10/04—Revision 0: Initial Version

Rev. 0 | Page 2 of 16

ADD8708

ELECTRICAL CHARACTERISTICS

VDD = 16 V, TA @ 25°C, unless otherwise noted.

Table 1.

Parameter Symbol Conditions Min Typ Max Unit

GAMMA CURVE CHARACTERISTICS

Accuracy R
Programming Resolution R
Total Resistor String R

BUFFER CHARACTERISTICS

OUTPUTS

Output Voltage Range (Ch18 to Ch10) V
Output Voltage Range (Ch9 to Ch1) V

Output vs. Load (Ch18, Ch17, Ch2, Ch1) ∆V
Output vs. Load (Ch16 to Ch3) ∆V

INPUTS

Offset Voltage V
Offset Voltage Drift ∆VOS/∆T

Input Bias Current I

Input Voltage Range (Ch18 to Ch10) V
Input Voltage Range (Ch9 to Ch1) V

DYNAMIC PERFORMANCE

Slew Rate SR RL = 10 kΩ, CL = 200 pF 4 6 V/µs
Bandwidth BW –3 dB, RL = 10 kΩ, CL = 200 pF 4.5 MHz
Settling Time to 0.1% t
Phase Margin Ф
Power Supply Rejection Ratio PSRR

VOLTAGE REGULATOR

Programmable Range V

Initial Regulator Accuracy V
Dropout Voltage V

I

Line Regulation REG
Load Regulation REG
Maximum Load Current I

Feedback Reference Voltage V

Feedback Input Bias Current I

SYSTEM ACCURACY

Total Error

3, 4

POWER SUPPLY

Supply Voltage V
Supply Current I

ACC

RES

TOTAL

OUT

OUT

OUT

OUT

OS

B

IN

IN

S

o

REG OUT

ACC

DO

O

REF

B FB

V

Total Error

DD

SY

1

2

2

LINE

LOADIO

0.1 0.4 %
500 segments 0.2 %
15 kΩ

IL = 100 µA 1.4 V
IL = 100 µA 0

DD

V

− 1.4

DD

V
V

IL = 20 mA 15 mV
IL = 5 mA 5 mV

5 15 mV

−40°C ≤ T

≤ +105°C

A

−40°C ≤ TA ≤ +105°C

1.4 V
0

20 µV/°C

0.5 1.5 µA

DD

V

− 1.4

DD

V
V

1 V, RL = 10 kΩ, CL = 200 pF 1.1 µs
RL = 10 kΩ, CL = 200 pF 55 Degrees

= 7 V to 17 V,

V

DD

−40°C ≤ T

≤ +105°C

A

5

No load; V

= 14.4V 0.4 1.5 %

REG OUT

68 90 dB

V

− 0.6

DD

V

IL = 100 µA 100 150 mV

= 5 mA 310 350 mV

L

VIN = 8.5 V to 16.5 V, V

= 8 V 0.01 0.20 %/V

OUT

= 100 µA to 10 mA 0.02 0.10 %/mA

−40°C ≤ TA ≤ +105°C

−40°C ≤ TA ≤ +105°C

−40°C ≤ TA ≤ +105°C

5 mA

1.2 V

-150 10 150 nA

0.5 3 %

7.5 16 V
No load; −40°C ≤ TA ≤ +105°C

9.5 16 mA

1

Gamma curve accuracy includes resistor matching and buffer errors, but excludes the regulator error.

2

∆V

is the shift from the desired output voltage under the specified current load.

OUT

3

Total error is the difference between the designed and actual output voltage divided by the actual regulator output voltage or full-scale voltage.

4

Total error includes regulator error, resistor string error, bias current effects, and buffer offset voltage.

Rev. 0 | Page 3 of 16

ADD8708

ABSOLUTE MAXIMUM RATINGS

Table 2.

Parameter Rating

Supply Voltage (VDD) 18 V
Input Voltage

Storage Temperature Range
Operating Temperature Range

1

−0.5 V to V

DD

−65°C to +150°C

−40°C to +105°C

Junction Temperature Range –65°C to +150°C
Lead Temperature Range (Soldering, 60 sec) 300°C
ESD Tolerance (HBM) ±1500 V
ESD Tolerance (MM) ±200 V

Table 3. Package Characteristics

Package Type θ

2

JA

3

θ

JA

Unit

LFCSP (CP) 28.3 47.7 °C/W
LQFP (ST) N/A 74.57 °C/W

1

See the section. Application Notes

2

θJA for exposed pad soldered to JEDEC 4-layer board.

3

θJA for exposed pad not soldered down.

Stresses above those listed under Absolute Maximum Ratings
may cause permanent 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.

ESD 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 this product 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 | Page 4 of 16

ADD8708

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

18

17

16

15

14

REG

V

REG OUT

GND

V

VIN18
V

IN

V

IN

V

IN

V

IN

V

IN

V

IN

V

IN

OUT

OUT

OUT

OUT

VDDGND

V

48 47 46 45 44 43 42 41 40 39 38 37

1

FB

2

3

DD

4

5

17

6

16

7

15

8

14

9

13

10

12

11

11

12

13 14 15 16 17 18 19 20 21 22 23 24

10

IN

V

9

8

7

IN

IN

IN

V

V

V

OUT

V

V

V

ADD8708

TOP VIEW

(Not to Scale)

6

5

4

IN

IN

IN

V

V

V

Figure 2. Pin Configuration

13

V

3
V

OUT

IN

12

11

DD

OUT

OUT

GND

V

V

2

IN

V

V

36

V

10

OUT

35

9

V

OUT

34

8

V

OUT

33

7

V

OUT

32

V

DD

GND

31

6

V

30

OUT

5

V

29

OUT

V

4

28

OUT

3

V

27

OUT

2

V

26

OUT

1

V

25

OUT

1

DD

IN

V

V

GND

04614-002

Table 4. Pin Function Descriptions

Pin No. Name Description

1 REG

FB

Regulator Feedback. Compares a percentage of the regulator output to the internal 1.2 V voltage

reference. Internal resistors are used to program the desired regulator output voltage.
2 GND Ground. Normally 0 V.
3 V
4 V

DD

REG OUT

Supply Voltage. Normally 16 V.

Regulator output voltage. Provides reference voltage to resistor string and is internally connected to

the top of the resistor string.
5 VIN18
6 VIN17
7 VIN16
8 VIN15
9 VIN14
10 VIN13
11 VIN12
12 VIN11
13 VIN10
14 VIN9

Buffer inputs. Normally floating.

1

15 VIN8
16 VIN7
17 VIN6
18 VIN5
19 VIN4
20 VIN3
21 VIN2
22 VIN1
23 GND Ground. Normally 0 V.
24 V

DD

Supply Voltage. Normally 16 V.

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 from your

local sales office.

Rev. 0 | Page 5 of 16