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| Evaluation Kit for LCD Power, VCOM, and Gate Modulation ADD8754-EVAL FEATURES Fully assembled evaluation board with test pins and standoffs User-selectable jumpers for easy configuration changes Optimized layout to reduce ground bounce and EMI Multiple ground test-pins for easy grounding Test pins labeled and segmented for each functional block PRODUCT DESCRIPTION The ADD8754-EVAL simplifies the evaluation of the ADD8754 device. It includes a fully assembled evaluation board and detailed usage instructions. This data sheet describes the ADD8754 evaluation board only. For specific information regarding the ADD8754 device, LCD power, VCOM, and gate modulation, see the ADD8754 data sheet. PACKAGE CONTENTS ADD8754 evaluation board 5 ADD8754 devices ADD8754 data sheet ADD8754-EVAL data sheet CD including Electronic version of ADD8754 data sheet Electronic version of ADD8754-EVAL data sheet Excel(R)-based spreadsheet for power dissipation calculations Excel-based spreadsheet for loop compensation components selection EVALUATION BOARD DIGITAL PICTURE Figure 1. Rev. A Evaluation boards are only intended for device evaluation and not for production purposes. Evaluation boards as supplied "as is" and without warranties of any kind, express, implied, or statutory including, but not limited to, any implied warranty of merchantability or fitness for a particular purpose. No license is granted by implication or otherwise under any patents or other intellectual property by application or use of evaluation boards. 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. Analog Devices reserves the right to change devices or specifications at any time without notice. Trademarks and registered trademarks are the property of their respective owners. Evaluation boards are not authorized to be used in life support devices or systems. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c)2006-2007 Analog Devices, Inc. All rights reserved. 06040-001 ADD8754-EVAL TABLE OF CONTENTS Features .............................................................................................. 1 Package Contents.............................................................................. 1 Product Description......................................................................... 1 Evaluation Board Digital Picture.................................................... 1 Revision History ............................................................................... 2 Evaluation Board Hardware ............................................................ 3 Quick Start Instructions .............................................................. 3 Factory Settings ............................................................................ 3 Jumper Selection........................................................................... 3 Basic Circuit ...................................................................................... 4 Functional Block Overview............................................................. 5 Step-Up Switching Regulator...................................................... 5 LDO.................................................................................................5 VCOM Amplifier ..........................................................................5 Gate Pulse Modulator ...................................................................5 AD5259 Digital Potentiometer (Optional) ................................6 Evaluation Board Layout ..................................................................7 Functional Blocks..........................................................................7 Layers ..............................................................................................8 Schematic..................................................................................... 10 Ordering Information.................................................................... 11 Component Listing .................................................................... 11 Ordering Guide .......................................................................... 12 ESD Caution................................................................................ 12 REVISION HISTORY 3/07--Rev. 0 to Rev. A Changes to Features Section............................................................ 1 Changes to Jumper Selection Section ............................................ 3 Changes to VCOM Amplifier Section ........................................... 5 Changes to Table 3............................................................................ 6 Changes to Component Listing Section...................................... 11 6/06--Revision 0: Initial Version Rev. A | Page 2 of 12 ADD8754-EVAL EVALUATION BOARD HARDWARE QUICK START INSTRUCTIONS Follow these steps to begin using the ADD8754 evaluation board: 1. 2. 3. Connect ground to at least one of the 10 pins labeled GND. Connect a 5 V power supply to at least one of the two pins labeled VIN. Apply a 2.5 V to 5 V digital control signal on VFLK. This control signal determines when VGH_M is at GPM_H or GPM_L. See the Gate Pulse Modulator section to determine a typical waveform. Table 2. LDO Output Voltage Jumper Selection Jumper Position Short Pin 2 and Pin 3 Open all pins Short Pin 1 and Pin 2 Description LDO_OUT = 3.3 V, see Figure 2. LDO_OUT = 2.85 V, see Figure 3. LDO_OUT = 2.5 V, see Figure 4. JP3 Figure 2. JP3 Short Pin 2 and Pin 3 FACTORY SETTINGS The ADD8754-EVAL arrives fully assembled and ready to use. The factory voltage settings are detailed in Table 1. See the Quick Start Instructions section for power-up instructions. Table 1. Factory Settings Test Point BOOST_OUT2 LDO_OUT VCOM VGH_M VDD_1 VGL 1 JP3 Figure 3. JP3 Open All Pins JP3 Value 9.8 V 3.3 V 4.9 V 28 V 9.8 V -5 V 1 Description Step-up output voltage LDO output voltage VCOM output voltage Gate pulse modulation output GPM low ramp voltage Gate low voltage Figure 4. JP3 Short Pin1 and Pin 2 JP4--VCOM Buffer Mode When the JP4 jumper is shorted, the VCOM negative input and output are shorted together. This configures VCOM as a unity gain buffer. Remove this jumper if external VCOM feedback is desired. JP5--VDPM from Step-Up When the JP5 jumper is shorted, the step-up output connects to VDPM. This enables GPM and requires no external signal on VDPM. Remove this jumper if an external VDPM control is desired. Actual voltages may differ slightly (3%). 2 Soft start time is 100 s when VIN = 5 V and 500 s when VIN = 3.3 V. JUMPER SELECTION The jumper pins are listed and described in this section. JP1--SHDN Control If the JP1 jumper is shorted, the SHDN pin is shorted to ground, causing the ADD8754 to shut down. When the jumper is opened, the ADD8754 continues to operate normally. If external shutdown control is desired, remove this jumper. JP6--VCOM Supply from Step-Up When the JP6 jumper is shorted, the VCOM supply (VDD_2) is connected to the step-up output. This eliminates the need for an external VCOM supply voltage. If the use of an external VCOM power supply is desired, remove this jumper and connect a power supply to VDD_2. JP2--FREQ Select If the JP2 jumper is shorted, the ADD8754 operates at a 650 kHz internal switching frequency. If this jumper is open, the device operates at 1.2 MHz. See the ADD8754 data sheet for details. JP7--VGH from Positive Charge Pump When the JP7 jumper is shorted, GPM receives its VGH voltage from the positive charge pump. If an external VGH voltage is desired, remove this jumper to drive the VGH pin externally. JP3--LDO Output Select The JP3 jumper has three positions (3.3 V, 2.85 V, and 2.5 V) for setting the LDO output voltage. Table 2 illustrates the proper jumper configuration. Rev. A | Page 3 of 12 06040-004 06040-003 After these steps are completed, users can probe the preconfigured output voltages and waveforms. 06040-002 ADD8754-EVAL BASIC CIRCUIT BAV99 VCPH VZ2 BZX84C28 R5 1k C7 1F C3 1F D5 D4 C4 1F D3 BAV99 D2 C2 0.1F C1 0.1F VCPL VZ1 BZX84C5V1 R6 300 R18 OPEN C6 1F BAV99 D6 D7 C5 0.1F R9 10 D1 1N5818 BOOST_OUT COUT1, COUT2, COUT3 10F, 10F, 0.1F JP7 LX FB FREQ VIN_1 VIN_2 L 10H VGH RE 33k RE CE GND PGND R1 71.5k VGH R11 100k FUSE VIN JP2 RSD 100k CIN1, CIN2 0.1F RC 180k CC 470pF CC1 30pF CSS 10nF LDO_OUT JP3 CLDO, C12 4.7F, 0.1F R2 10k JP1 SHDN CIN 10F CE 1nF VGH_M VFLK VDP JP5 BOOST_OUT R7 47k R8 8.2k C8 OPEN VGH_M VFLK VDPM SHDN ADD8754 COMP VDD_1 R24 15k VDD_2 VCOM C13 OPEN R13 OPEN R12 10k R23 OPEN R4 20k JP6 VDD_2 VCOM NEG POS SS LDO_OUT ADJ AGND R10 OPEN V_LOAD JP4 C19 OPEN Figure 5. Basic Board Circuit with Factory-Installed Component Rev. A | Page 4 of 12 06040-005 C18 4.7F ADD8754-EVAL FUNCTIONAL BLOCK OVERVIEW This section provides an overview of the important features of each functional block to assist in evaluating the ADD8754 device. For detailed information about the ADD8754, see the ADD8754 data sheet. See Table 1 for a list of factory voltage settings. When reviewing this section, keep the following points in mind: * * * * The ADD8754 has an undervoltage lockout circuit that prevents operation below a VIN of 2.8 V. The high-side charge pump has a Zener diode regulated output (VCPH) of 28 V. The low-side charge pump has a Zener diode regulated output (VCPL) of -5 V. The evaluation board shuts down when the SHDN pin is connected to ground (JP1 is shorted). LDO The LDO generates a selectable logic voltage output for the digital logic needs of a TFT-LCD display. Typically, this voltage is applied to the timing controller (TCON) and gate drivers. For instructions on selecting the 3.3 V, 2.85 V, or 2.5 V voltage output, see Table 2. VCOM AMPLIFIER Buffer and Feedback Configurations The VCOM amplifier of the ADD8754 can be used as a unitygain buffer or with panel feedback. To set the ADD8754 in a unity-gain buffer configuration, short Jumper JP4. Please note that if using model ADD8754ACPZ, buffer mode is not recommended. To use panel feedback, open Jumper JP4 and use the VCOM_S pin, Resistor R16, Resistor R17, Capacitor C16, and Capacitor C17 to configure the feedback network. To add VCPL feedback, R14, R15, C14, and C15 can be changed. R13, R21, C13, and C22 are used to set the VCOM amplifier gain. R10 and C9 are used if a filtered output is desired from the VCOM amplifier. STEP-UP SWITCHING REGULATOR The step-up switching regulator, or boost converter, converts a dc voltage input of 5 V to an output of 10 V (adjustable up to 20 V). With its factory setting, the boost converter can output up to 750 mA of load current. Typically, a TFT-LCD monitor requires about 500 mA of current at 10 V. For an accurate evaluation of the step-up regulator, it is recommended that an equivalent panel load (20 to 40 ) be applied from BOOST_OUT to GND. Adjusting VCOM The reference voltage for VCOM is adjustable by turning the on-board potentiometer (Potentiometer R12) using a small screwdriver. The VCOM voltage range depends on the boost output voltage and how it is divided by Resistor R24, Resistor R4, and Resistor R12. If your board includes an AD5259 256-position digital potentiometer, this device is configured for use (the analog potentiometer is disabled). See the AD5259 Digital Potentiometer (Optional) section for details about setting and disabling this device. For more information about the AD5259, see the AD5259 data sheet. Resetting the Boost Output Voltage BOOST_OUT is determined by the divider resistors R1 and R2. To obtain a given output, set R2 = 10 k and calculate R1 = R2 x (BOOST _ OUT - 1.21) 1.21 Loop Compensation Resistor RC and Capacitor CC set the loop compensation for stability. If the input voltage, output voltage, inductor, or output capacitor values need to be changed, see the ADD8754 data sheet for a method tPo recalculate the compensation values for stable operation of the step-up switching regulator. GATE PULSE MODULATOR The gate pulse modulator takes a high voltage (VGH) and ramps this voltage down to a lower voltage (VDD_1). The VFLK signal determines when the voltage begins ramping. The CE capacitor and RE resistor determine the delay and the ramp rate. VDPM must be pulled high to enable GPM (Jumper JP5 should be shorted). A startup delay for VGH_M can be set with C8. Inductor Current Rating The factory-installed inductor is rated for 1.5 A. If the output current and/or output voltage make the inductor current higher than 1.5 A, then the inductor should be replaced with an appropriate inductor to prevent saturation. Soft Start The soft start time is adjusted by Capacitor CSS. See the ADD8754 data sheet for instructions on recalculating a new soft start time. Rev. A | Page 5 of 12 ADD8754-EVAL Setting VDD_1 The VDD_1 voltage is the GPM low ramp voltage. With R25 shorted and RZ open, the step-up output (BOOST_OUT) is connected to VDD_1. This ramps the GPM_H waveform down to the BOOST_OUT voltage level. If other voltages are desired, a voltage divider or Zener diode can be used to set this voltage. If a voltage divider is used, a low divider impedance (<1 k) is recommended. See the ADD8754 data sheet for more information. Table 3. AD5259 Component Differences Label C13 C23 R12 R13 R21 R22, R23 R24 R_SCA, R_SCL Description VCOM feedback capacitor AD5259 VDD bypass capacitor Variable resistor for VCOM positive input VCOM feedback resistor VCOM negative input resistor AD5259 digital control pull-up resistor VCOM positive input divider resistor (top) AD5259 digital control series resistors Value Open Open 10 k Open Open Open 15 k Open Adjusting the Delay and Ramp Rate Capacitor CE adjusts the negative ramp delay of the VGH_M waveform. RE adjusts the negative ramp rate of the VGH_M waveform. See the ADD8754 data sheet for details. To use the programmable potentiometer 1. 2. 3. 4. 5. Connect the ADD8754-EVAL to the parallel port of a PC using a parallel port cable. Insert the CD from the evaluation kit into the CD drive and click setup.exe to install the software. Once installation is complete, open the AD5259 Evaluation Board Program from the Start menu. Enter data in the Enter Data text box and then click Write to RDAC to write the data. Click the Store RDAC Content to EEMEM button to store the current RDAC setting to EEMEM. VFLK Input The amplitude of the input signal on VFLK must be between 2.5 V to 5.0 V. Typically, VFLK is a digital waveform that switches from high to low for each horizontal line of the TFT-LCD display (from TCON). If a signal generator is used, the following settings are recommended to simulate a 1280 x 1024 60 Hz panel: * * * * Digital pulse signal 3.3 V amplitude (low = 0 V, high = 3.3 V) 16 s period 30% duty cycle AD5259 DIGITAL POTENTIOMETER (OPTIONAL) If the ADD8754-EVAL includes an optional AD5259 digital potentiometer, the VCOM output voltage is set by using Resistor R3, Resistor R4 and the programmed output resistance of the 10 k digital potentiometer, AD5259. Set the components as shown in Table 3. Note that because the AD5259 is a low voltage part (supply from LDO_OUT), the appropriate VCOM gain resistors must be configured to raise the VCOM output voltage. If Resistor R13 and Resistor R21 are set to the values listed in Table 3, the gain is set to +3. For more information, see the AD5259 Evaluation Board User Manual on the ADD8754 Evaluation Kit CD. Rev. A | Page 6 of 12 ADD8754-EVAL EVALUATION BOARD LAYOUT FUNCTIONAL BLOCKS BLOCK 1 BLOCK 8 BLOCK 2 BLOCK 7 BLOCK 10 BLOCK 9 BLOCK 3 BLOCK 6 BLOCK 5 BLOCK 4 Figure 6. Evaluation Board Layout Table 4. Evaluation Board Functional Block Descriptions Block 1 2 3 4 5 6 7 8 9 10 Description Positive Charge Pump. Provides access to the positive charge pump output (VCPH) and ground. Gate Pulse Modulation. Accepts digital inputs from the timing controller (TCON) and provides a modulated VGH waveform (VGH_M). VCOM Amplifiers. Provides access to the VCOM amplifier. The potentiometer in Block 9 adjusts the VCOM voltage. AD5259 Serial Port. Accepts a serial port. Only boards with the optional AD5259 digital potentiometer include this port. LDO. Provides access to the LDO output. Digital Potentiometer. For digital control of the AD5259. Only boards equipped with the optional AD5259 use this pin. Power Supply. Accepts an input voltage and provides the step-up output voltage (BOOST_OUT) and various ground pins. Negative Charge Pump. Provides access to the negative charge pump output (VCPL) and ground. VCOM Potentiometer. Includes one analog potentiometer configured in a rheostat mode for VCOM adjustment. ADD8754. Includes a soldered ADD8754 24-lead LFCSP. If the part needs to be replaced, care should be taken to properly solder the thermal vias to the thermal pad on the bottom side of the IC. Rev. A | Page 7 of 12 06040-006 ADD8754-EVAL LAYERS Figure 7. Evaluation Board Layout--Top Layer Rev. A | Page 8 of 12 06040-007 ADD8754-EVAL Figure 8. Evaluation Board Layout--Bottom Layer Table 5. Evaluation Board Layer Descriptions Layer Blue (Top) Red (Bottom) Description Top-of-board metal traces and ground plane. See Figure 7. Bottom-of-board metal traces and ground plane. Note that the top-view is shown in Figure 8. Silkscreen text is shown for orientation purposes only; text does not appear on bottom of board. Rev. A | Page 9 of 12 06040-008 ADD8754-EVAL SCHEMATIC Figure 9. Evaluation Board Rev. A | Page 10 of 12 06040-009 ADD8754-EVAL ORDERING INFORMATION COMPONENT LISTING Table 6. Qty. 2 2 1 1 1 1 1 1 1 1 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 1 1 2 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Reference Designator C1, C2 C3, C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 1 C14, C15 C16 C17 C18 C22 C231 C24 CC CC1 CE CIN CIN1 CIN2 CLDO COUT1, COUT2 COUT3 CSS D1 D2/D3 D4/D5 D6/D7 FUSE JP1 JP2 JP3 JP4 JP5 JP6 JP7 L1 R1 R2 R31 R4 R5 R6 R7 R8 Description Positive charge pump flying capacitors Positive charge pump charging capacitors Negative charge pump flying capacitor Negative charge pump charging capacitor Negative charge pump filter capacitor VPDM start-up delay capacitor VCOM load capacitor VDD_2 (VCOM supply) bypass capacitor VDD_1 (GPM low) bypass capacitor LDO output bypass capacitor VCOM feedback capacitor VCOM VGH feedback capacitors VCOM sense feedback capacitor VCOM sense feedback capacitor VCOM positive input bypass capacitor VCOM feedback capacitor AD5259 VDD bypass capacitor VDD_1 filter capacitor Step-up loop compensation capacitor Step-up loop compensation capacitor GPM negative ramp delay capacitor VIN_1 and VIN_2 bypass capacitor VIN_1 bypass capacitor VIN_2 bypass capacitor LDO output capacitor Step-up output (charging) capacitors Step-up output capacitor Soft-start capacitor Step-up converter diode Positive charge pump doubler diodes Positive charge pump tripler diodes Negative charge pump diodes Input supply fuse SHDN jumper FREQ select jumper LDO output select jumper VCOM buffer configuration jumper VDPM from step-up jumper VCOM supply from step-up jumper Positive charge pump to VGH Step-up converter inductor Step-up feedback divider resistor (top) Step-up feedback divider resistor (bottom) AD5259 divider resistor (top) VCOM positive input divider resistor (bottom) Positive charge pump current limiting resistor Negative charge pump current limiting resistor VDPM step-up voltage divider resistor (top) VDPM step-up voltage divider resistor (bottom) Rev. A | Page 11 of 12 Value 0.1 F 1 F 0.1 F 1 F 1 F Open Open 0.1 F 0.1 F 0.1 F Open Open Short Open 4.7 F Open Open Open 470 pF 30 pF 1 nF 10 F 0.1 F 0.1 F 4.7 F 10 F 0.1 F 10 nF 1N5818 BAV99WT1 BAV99WT1 BAV99WT1 1A Open Short Short 1 and Short 2 Short Short Short Short 10 H 71.5 k 10 k Open 20 k 1 k 300 47 k 8.2 k ADD8754-EVAL Qty. 1 1 1 1 1 2 1 1 1 1 2 1 1 1 1 2 1 1 1 1 1 1 1 Reference Designator R9 R10 R11 R121 R131 R14, R15 R16 R17 R18 R211 R221, R231 R241 R25 RC RE R_SCA1, R_SCL1 RSD RZ U1 U2 VZ1 VZ2 Description Charge pump surge current limiting resistor VCOM series load resistor FREQ select pull-up resistor Variable resistor for VCOM positive input VCOM feedback resistor VCOM VGH feedback resistors VCOM sense feedback resistor VCOM sense feedback resistor VGH output voltage divider resistor (bottom) AD5259 VCOM negative input resistor AD5259 digital control pull-up resistors VCOM positive input divider resistor (top) VDD_1 (GPM low) resistor divider (top) Step-up loop compensation resistor GPM negative ramp rate (slope) resistor AD5259 digital control series resistors SHDN pull-up resistor VDD_1 (GPM low) resistor divider (bottom) ADD8754 24-lead LFCSP AD5259 8-lead SOIC Negative charge pump output Zener diode Positive charge pump output Zener diode Value 10 Open 100 k 10 k Open Open Short Open Open Open Open 15 k Short 180 k 33 k Open 100 k Open ADD8754 AD5259 BZX84C5V1 BZX85C28 These component values must be changed when using the AD5259 digital potentiometer. ORDERING GUIDE Model ADD8754-EVAL Description Evaluation Kit ESD CAUTION (c)2006-2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. EB06040-0-3/07(A) Rev. A | Page 12 of 12 |
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