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12-Channel Gamma Buffers with VCOM Buffer ADD8702 FEATURES Programmable 12-Channel Gamma Reference Generator Mask Programmable Adjustable VCOM Buffer Upper/Lower Outputs Swing to VDD/GND Continuous Output Current: 10 mA VCOM 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 VCOM OUT VGMA12 VGMA11 VGMA10 VGMA9 VGMA8 26 32 31 30 26 28 27 25 24 23 22 21 20 19 18 17 VDD VCOM ADJ VHIGH VIN11 VIN10 VIN9 VIN8 VIN7 VGMA7 GND 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 GND VDD VGMA6 VGMA5 VGMA4 VGMA3 VGMA2 VGMA1 VLOW VIN6 VIN5 VIN4 VIN3 VIN2 VDD The ADD8702 is a low cost, mask programmable, 12-channel gamma reference generator, plus an adjustable VCOM driver. This part is designed to provide gamma correction for high resolution TFT LCD panels. The 12 gamma reference levels and VCOM 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 VCOM output is stable with high capacitive loads and can source or sink 250 mA peak current. The VCOM 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 -40C to +85C and comes in the 32-lead lead frame chip scale package (LFCSP) for compact board space. PANEL TIMING CONTROLLER ADD8702 TIMING AND CONTROL GAMMA REFERENCE VOLTAGES GAMMA VCOM SCAN DRIVER CONTROL SOURCE DRIVER NO. 1 384 SOURCE DRIVER NO. 2 384 SOURCE DRIVER NO. 8 384 RGB 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 (c) 2003 Analog Devices, Inc. All rights reserved. GND GENERAL DESCRIPTION ADD8702-SPECIFICATIONS ELECTRICAL CHARACTERISTICS (V Parameter OUTPUT ACCURACY VSYSTEM 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 VCOM CHARACTERISTICS Continuous Output Current Peak Output Current Settling Time--Voltage SUPPLY CHARACTERISTICS Supply Voltage Power Supply Rejection Ratio SUPPLY CURRENT Symbol VSY ERROR DD = 16 V, TA = 25 C, unless otherwise specified.) Min Typ 10 Max 50 Unit mV Conditions RTOTAL RMATCH VOUT VOUT VOUT IOUT IPK tS IOUT IPK tS VDD PSRR ISYS 500 Elements VLOW to VHIGH Any Two Segments IL = 100 A IL = 5 mA -40C TA +85C IL = 5 mA IL = 100 A IL = 5 mA -40C TA +85C 1 V Step 0.1%, RL = 10 k, CL = 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 k % V V V V mV mV mV mA mA s mA mA s V dB mA mA 15.85 15.75 150 250 1 V Step 0.1%, RL = 10 k, CL = 200 pF VS = 6 V to 17 V, -40C TA +85C No Load -40C TA +85C Specifications subject to change without notice. -2- REV. 0 ADD8702 ABSOLUTE MAXIMUM RATINGS* Supply Voltage (VS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 V Storage Temperature Range . . . . . . . . . . . . . -65C to +150C Operating Temperature Range . . . . . . . . . . . . -40C to +85C Junction Temperature Range . . . . . . . . . . . . . -65C to +150C Lead Temperature Range (Soldering, 60 sec.) . . . . . . . . 300C ESD Tolerance (HBM) . . . . . . . . . . . . . . . . . . . . . . . 1,000 V *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. Package Type 32-Lead LFCSP (CP) JA 1 2 JB Unit C/W 35 13 NOTES 1 JA is specified for worst-case conditions, i.e., JA is specified for device soldered in circuit board for surface-mount packages. 2 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 -40C to +85C -40C to +85C -40C to +85C Package Description 32-Lead LFCSP 32-Lead LFCSP 32-Lead LFCSP Package Option CP-32 CP-32 CP-32 PIN CONFIGURATION 32 VCOM OUT 31 GND 30 VGMA12 29 VGMA11 28 VGMA10 27 VGMA9 26 VGMA8 25 VGMA7 VDD 1 VCOM ADJ 2 VHIGH 3 VIN11 4 VIN10 5 VIN9 6 VIN8 7 VIN7 8 PIN 1 INDICATOR ADD8702 TOP VIEW 24 GND 23 VDD 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 VDD VCOM ADJ VHIGH VIN11-VIN2 VLOW GND VGMA1-VGMA12 VCOM 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 VIN6 9 VIN5 10 VIN4 11 VIN3 12 VIN2 13 VLOW 14 VDD 15 GND 16 Description Power (+) VCOM Adjust Input Highest Gamma Input Voltage Gamma Buffer Inputs Lowest Gamma Input Voltage Power (-) Gamma Buffer Outputs VCOM Buffer Output -3- ADD8702-Typical Performance Characteristics 12 TA = 25 C 10 12 VDD = 16V 11 SUPPLY CURRENT (mA) 10 VDD = 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 VDD = 16V GAMMA 10 TO 12 0 2k , 10k 10 VDD = 16V VCOM 2k , 10k -10 20 VDD = 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 VDD = 16V GAMMA 10 TO 12 10 20 VDD = 16V VCOM 180 160 PHASE SHIFT (Degrees) 10 VDD = 16V GAMMA 1 TO 12 RL = 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 VDD = 16V RL = 10k CL = 100pF 14 12 VDD = 16V RNULL = 33 CL = 100pF 10 VCOM SLEW RATE FALLING 8 VCOM SLEW RATE RISING 6 4 2 0 -40 VOLTAGE (20mV/DIV) SLEW RATE (V/ s) VOLTAGE (2V/DIV) 7V < V DD < 16V RNULL = 33 CL = 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 VDD = 16V GAMMA = 2 11 10 9 VDD = 16V GAMMA = 11 11 10 9 VDD = 16V VCOM 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) VDD = 16V 90 GAMMA 1 TO 9 1,400 1,200 1,000 800 600 400 200 VDD = 16V GAMMA 10 TO 12 SINK 50 VDD = 16V 45 VCOM 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- ADD8702 6,000 80 POWER SUPPLY REJECTION RATIO (dB) FREQUENCY (No. of Amplifiers) VDD = 16V TA = 25 C 5,000 ALL CHANNELS 4,000 60 40 20 0 -20 -40 ALL CHANNELS VDD = 8V TA = 25 C VOLTAGE (3V/DIV) 3,000 2,000 PSRR -60 -80 -100 -120 100 1k 10k 100k FREQUENCY (Hz) 1M 10M 1,000 0 -22 -14 -6 2 10 18 26 OUTPUT VOLTAGE ERROR (mV) 34 TIME (40 s/DIV) TPC 19. Output Voltage Error Distribution TPC 20. Power Supply Rejection Ratio vs. Frequency TPC 21. No Phase Reversal 70 70 VOLTAGE NOISE DENSITY (nV/ Hz) 60 50 40 30 20 10 0 -10 VOLTAGE NOISE DENSITY (nV/ Hz) VDD = 16V VCOM AND BUFFERS 1 TO 9 MARKER SET @ 10kHz MARKER READING = 25.7nV/ Hz 60 50 40 30 20 10 0 -10 VDD = 16V BUFFERS 10 TO 12 MARKER SET @ 10kHz MARKER READING = 36.6nV/ Hz 0 5 10 15 FREQUENCY (Hz) 20 25 0 5 10 15 FREQUENCY (Hz) 20 25 TPC 22. Voltage Noise Density vs. Frequency TPC 23. Voltage Noise Density vs. Frequency -6- REV. 0 ADD8702 APPLICATIONS Figure 1 is a block diagram of the configuration of an XGAcompatible (1024 768) TFT color panel with the ADD8702 providing gamma correction reference voltages to the source drivers and an integrated VCOM driver for LCD common node. 16V BUFFER RNULL CT RL VHIGH A12 GMA 12 VIN11 A11 GMA 11 VIN10 A10 GMA 10 VIN9 A9 GMA 9 Figure 2. Bandwidth Measurement Information VIN5 A5 GMA 5 16V 0.1 s BUFFER 5V 33 1k VTH VTH 10V 5V 0V VIN4 A4 GMA 4 VIN3 A3 GMA 3 Figure 3. Transient Load Regulation Test Circuit The ADD8702 is designed to meet the rail-to-rail capability needed by the application, yet offers the lowest cost per channel solution. The ADD8702 gamma buffers offer 10 mA continuous drive current capability. To be more competitive, the design maximizes the die area by allowing specific channels to swing to the positive rail and negative rail. So it is imperative that the channels swinging close to the supply rail be used for the positive gamma references and the channels swinging close to GND be used for the negative gamma references. The VCOM buffer can handle up to 35 mA continuous output current and can drive up to 1,000 pF pure capacitive load. Provision is available to adjust the VCOM voltage to a desired level. Refer to Figure 4 for an example of an application circuit for adjusting the output of the VCOM buffer. VIN2 A2 GMA 2 VLOW VDD A1 GMA 1 LCD SOURCE DRIVER VCOM AMP LCD COMMON PLANE 32k GND VCOM ADJUST 2k ADD8702 Figure 4. Application Circuit Table I. ADD8702 - 000 Mask Option, Resistor Tap Points (0 500) VDD = 12.5 V, VHIGH = 12.5 V, and VLOW = GND Tap Point ( ) VGMA1 VGMA2 VGMA3 VGMA4 VGMA5 VGMA6 VGMA7 VGMA8 VGMA9 VGMA10 VGMA11 VGMA12 VCOM 8 57 84 115 139 194 218 298 371 418 442 488 200 Voltage 0.2 1.43 2.11 2.89 3.48 4.86 5.45 7.45 9.29 10.45 11.04 12.2 5 Unit V V V V V V V V V V V V V REV. 0 -7- NEGATIVE GAMMA REFERENCES Panel size and resolution determine the number of gamma reference voltages required. For a 256-grayscale level, 8-bit color scheme, 6 2 external reference nodes should be sufficient to match the characteristics of the LCD driver to the characteristics of the actual LCD panel for improved picture quality. External reference gamma correction voltages are often generated using a simple resistor ladder. Using the ADD8702, the resistor ladder is incorporated in the IC for reduced cost and number of components. VIN8 A8 GMA 8 VIN7 A7 GMA 7 VIN6 A6 GMA 6 POSITIVE GAMMA REFERENCES ADD8702 OUTLINE DIMENSIONS 32-Lead Lead Frame Chip Scale Package [LFCSP] (CP-32) Dimensions shown in millimeters 5.00 BSC SQ 0.60 MAX 0.60 MAX 25 24 32 1 PIN 1 INDICATOR PIN 1 INDICATOR TOP VIEW 4.75 BSC SQ 0.50 BSC BOTTOM VIEW 3.25 3.10 SQ 2.95 8 0.50 0.40 0.30 17 16 9 12 MAX 0.80 MAX 0.65 NOM 0.05 MAX 0.02 NOM 3.50 REF 1.00 0.90 0.80 SEATING PLANE 0.30 0.23 0.18 0.20 REF COPLANARITY 0.08 COMPLIANT TO JEDEC STANDARDS MO-220-VHHD-2 -8- REV. 0 C03820-0-6/03(0) |
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