MAX8784 19-0737 Rev 0 1/07 Step-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs General Description Features Step-Up Regulator Supply for LCD Panel Source The MAX8784 generates supply rails for the thin-film Driver transistor (TFT) liquid-crystal display (LCD) panels in TVs Fast Transient Response to Pulsed Load and monitors. It includes a step-up regulator, a regulated Built-In 18V, 4A, 0.11 n-Channel Power positive and a negative charge-pump, three high-current MOSFET with Lossless Current Sensing operational amplifiers, and Dual Mode, logic-con- Cycle-by-Cycle Current-Limit Comparator trolled, high-voltage switch control block. HVS mode 90% Efficiency (5V In to 15V Out) automatically increases the output voltages of the boost 1.2MHz Switching Frequency regulator and the positive charge-pump to stress test Three High-Current 19V Operational Amplifiers display panels during production. The MAX8784 can 180mA Output Short-Circuit Current operate from input voltages of 4V to 5.5V and is opti- 45V/s Slew Rate mized for LCD TV panel and LCD monitor applications. 20MHz Bandwidth The step-up DC-DC regulator provides a regulated sup- Rail-to-Rail Input and Output Operation ply voltage for TFT source drivers. The step-up regulator Regulated Charge-Pump Tripler with Integrated is a high-frequency (1.2MHz), high-efficiency, current- Diodes for TFT Gate-On Supply mode regulator. The step-up regulator has a built-in Regulated Charge Pump for TFT Gate-Off Supply 110m (typ) power MOSFET. The high-switching fre- Built-In Sequencing quency allows the use of ultra-small inductors and Internal Digital Soft-Start ceramic capacitors. The current-mode architecture pro- 36V Gate-On Switch vides fast transient response and easy compensation. Startup Timing Capacitors for AVDD and GON The step-up regulator features output undervoltage pro- Undervoltage and Thermal Protection tection, soft-start, internal current limit, and adjustable output voltage by an external resistive divider. 4V to 5.5V Input Operating Range The three operational amplifiers drive the LCD back- plane and the gamma-correction-divider string. Each Simplified Operating Circuit operational amplifier has a fast slew rate (45V/s), a wide bandwidth (20MHz), and a high-output short-cir- STEP-UP VIN OUTPUT cuit current (200mA). Each op amp has rail-to-rail input and rail-to-rail output operation. The positive charge-pump regulator and the negative LX V CC POS1 charge-pump regulator provide regulated supply volt- PGND TO NEG1 VCOM ages for the TFT gate drivers. The positive charge OUT1 pump is a two-stage charge pump, which requires no FB STEP-UP POS2 OUTPUT TO external diodes. The output voltages of both charge NEG2 COMP VCOM OUT2 pumps are resistor adjustable. The logic-controlled high-voltage switch allows the manipulation of the posi- POS3 RSET TO tive TFT gate-driver supply. VCOM OUT3 GDEL The MAX8784 is available in a small (5mm x 5mm), low- ADEL VIN HVS profile (0.8mm), 40-pin TQFN package and operates REF over the -40C to +85C temperature range. MAX8784 CTL TCON AGND Applications SHDN ON/OFF FBN GON VGON LCD TVs and LCD Monitors DRN VGOFF Ordering Information POUT DRVN PIN- PART TEMP RANGE PKG CODE PGND STEP-UP PACKAGE FBP OUTPUT 40 TQFN C1N C1P C2N C2P SUP MAX8784ETL+ -40C to +85C T4055-1 5mm x 5mm STEP-UP +Denotes a lead(Pb)-free/RoHS-compliant package. OUTPUT Dual Mode is a trademark of Maxim Integrated Products, Inc. Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com. EVALUATION KIT AVAILABLEStep-Up Regulator, Internal Charge Pumps, Switch Control, and Operational Amplifier for TFT LCDs ABSOLUTE MAXIMUM RATINGS V , CTL, HVS, SHDN, ADEL, GDEL to AGND ....-0.3V to +7.5V DRN to GON............................................................-30V to +30V CC REF Short Circuit to AGND.........................................Continuous REF, COMP, FB, FBN, FBP to AGND.........-0.3V to (V + 0.3V) CC POS1, NEG1, POS2, NEG2, POS3, OUT1, OUT2, RMS V Current................................................................50mA CC RMS DRVN Current...........................................................400mA OUT3 to AGND .......................................-0.3V to (V + 0.3) SUP LX, PGND RMS Current Rating.............................................2.4A PGND, BGND to AGND.........................................-0.3V to +0.3V LX, RSET to PGND .................................................-0.3V to +22V Continuous Power Dissipation (T = +70C) A 40-Pin TQFN (derate 35.7mW/C above +70C) .......2857mW SUP to AGND .........................................................-0.3V to +22V DRVN to AGND.........................................-0.3V to (V + 0.3V) Operating Temperature Range ...........................-40C to +85C SUP Junction Temperature......................................................+150C C1N, C2N to AGND ..................................-0.3V to (V + 0.3V) SUP Storage Temperature Range .............................-65C to +160C C1P to AGND .........................................................-0.3V to +30V POUT to C2P, C1P to C2P......................................-0.3V to +22V Lead Temperature (soldering, 10s) .................................+300C Soldering Temperature (reflow) .......................................+260C C2P, POUT to AGND..............................................-0.3V to +40V GON, DRN to AGND ..............................................-0.3V to +40V Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (V = +5V, Circuit of Figure 1, AVDD = SUP = +14V, T = 0C to +85C. Typical values are at T = +25C, unless otherwise noted.) CC A A PARAMETER CONDITIONS MIN TYP MAX UNITS V Input Supply Range 4.0 5.5 V CC V Undervoltage Lockout Threshold V rising, typical hysteresis = 50mV 2.4 2.6 2.8 V CC CC V = 1.3V, not switching 1.0 FB V = 1.1V, switching, no load, V disconnected, FB SUP V Quiescent Current 46 mA CC V = V , V = 0V FBP CC FBN SHDN = GND 0.05 SHDN Input Low Voltage 0.8 V SHDN Input High Voltage 1.8 V SHDN Input Current -1 +1 A REFERENCE REF Output Voltage No external load 1.238 1.250 1.262 V REF Load Regulation 0 < I < 50A 10 mV LOAD REF Sink Current In regulation 10 A REF Undervoltage Lockout Threshold Rising edge, typical hysteresis = 200mV 1.0 1.15 V OSCILLATOR AND TIMING Frequency 1000 1200 1400 kHz Oscillator Maximum Duty Cycle 87 90 93 % Duration to Trigger Fault Condition 47 55 65 ms ADE L, GD E L C apac i tor C har g e C ur r ent 4 5 6 A ADEL, GDEL Turn-On Threshold 1.25 1.32 V STEP-UP REGULATOR FB = COMP, C = 1nF 1.235 1.246 1.256 COMP FB Regulation Voltage V FB = COMP, C = 1nF, +25C to +85C 1.238 1.246 1.256 COMP FB Fault-Trip Level Falling edge 0.96 1.00 1.04 V FB Load Regulation 0 < I < full -1 % LOAD FB Line Regulation V = 4.5V to 5.5V 0.25 %/V CC FB Input Bias Current V = 1.25V 100 200 nA FB 2 MAX8784