MAX8740 19-3698 Rev 0 5/05 TFT-LCD Step-Up DC-DC Converter General Description Features The MAX8740 is a high-performance, step-up DC-DC 90% Efficiency converter that provides a regulated supply voltage for Adjustable Output from V to 28V IN active-matrix, thin-film transistor (TFT), liquid-crystal displays (LCDs). The MAX8740 incorporates current- 2.6V to 5.5V Input Supply Range mode, fixed-frequency, pulse-width modulation (PWM) Input Supply Undervoltage Lockout circuitry with a built-in n-channel power MOSFET to achieve high efficiency and fast transient response. Pin-Programmable 640kHz/1.2MHz Switching Users can select 640kHz or 1.2MHz operation using a Frequency logic input pin (FREQ). The high switching frequencies Programmable Soft-Start allow the use of ultra-small inductors and low-ESR ceramic capacitors. The current-mode architecture pro- 0.1A Shutdown Current vides fast transient response to pulsed loads. A com- Small, 10-Pin Thin DFN Package pensation pin (COMP) gives users flexibility in adjusting loop dynamics. The 30V internal MOSFET can generate output voltages up to 28V from a 2.6V and 5.5V input voltage range. Soft-start slowly ramps the input current and is programmed with an external capacitor. The MAX8740 is available in a 10-pin thin DFN package. Applications Ordering Information Notebook Computer Displays PART TEMP RANGE PIN-PACKAGE LCD Monitor Panels MAX8740ETB -40C to +85C 10 TDFN 3mm x 3mm Pin Configuration Minimal Operating Circuit V IN V OUT 2.6V TO 5.5V TOP VIEW 67 10 9 8 7 6 LX LX 8 2 FB IN MAX8740 9 5 MAX8740 GND FREQ 4 3 GND SHDN 10 1 1 2 3 4 5 COMP SS THIN DFN 3mm x 3mm Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com. EVALUATION KIT AVAILABLE COMP SS FB FREQ SHDN IN GND LX GND LXTFT-LCD Step-Up DC-DC Converter ABSOLUTE MAXIMUM RATINGS LX to GND ..............................................................-0.3V to +30V Operating Temperature Range ...........................-40C to +85C IN, SHDN, FREQ, FB to GND ...................................-0.3V to +6V Junction Temperature......................................................+150C COMP, SS to GND.......................................-0.3V to (V + 0.3V) Storage Temperature Range .............................-65C to +160C IN LX Switch Maximum Continuous RMS Current.....................2.4A Lead Temperature (soldering, 10s) .................................+300C Continuous Power Dissipation (T = +70C) A 10-Pin TDFN (derate 24.1mW/C above +70C).......1481.5mW 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 = V = 3V, T = 0C to +85C. Typical values are at T = +25C, unless otherwise noted.) IN SHDN A A PARAMETER CONDITIONS MIN TYP MAX UNITS V < 18V 2.6 5.5 OUT Input Voltage Range V 18V < V < 24V 4.0 5.5 OUT Output Voltage Range 28 V IN Undervoltage-Lockout V rising, typical hysteresis is 50mV LX remains off IN 2.20 2.38 2.57 V Threshold below this level V = 1.3V, not switching 0.22 0.44 FB IN Quiescent Current mA V = 1.0V, switching, FREQ = GND 2 5 FB IN Shutdown Current SHDN = GND 0.1 10.0 A ERROR AMPLIFIER FB Regulation Voltage Level to produce V = 1.24V 1.22 1.24 1.26 V COMP FB Input Bias Current V = 1.24V 50 125 250 nA FB FB Line Regulation Level to produce V = 1.24V, V = 2.6V to 5.5V 0.05 0.15 %/V COMP IN Transconductance 100 200 315 S Voltage Gain 2400 V/V OSCILLATOR FREQ = GND 540 640 740 Frequency kHz FREQ = IN 1000 1220 1500 Maximum Duty Cycle 88 91 94 % n-CHANNEL MOSFET Current Limit V = 1V, 71% duty cycle 3.9 4.6 5.3 A FB V = 3V (typ value at T = +25C) 0.11 0.17 IN A On-Resistance V = 5V (typ value at T = +25C) 0.095 0.15 IN A Leakage Current V = 28V 30 55 A LX Current-Sense Transresistance 0.09 0.15 0.25 V/A SOFT-START Reset Switch Resistance 100 Charge Current V = 1.2V 2.5 4.5 7.5 A SS 2 MAX8740