MAX8739

The MAX8739 includes a high-performance, step-up regulator and two high-current operational amplifiers for active-matrix thin-film transistor (TFT) liquid-crystal displays (LCDs). The input supply voltage range of the MAX8739 is from 1.8V to 5.5V. The device also includes a logic-controlled, high-voltage switch with adjustable delay.

Features of the MAX8739 are:(1)1.8V to 5.5V input supply range; (2)fast transient response to pulsed load; (3)high-accuracy output voltage (1.5%); (4)built-in 14V, 1.9A, 0.2 n-channel MOSFET; (5)high efficiency (> 85%); (6)digital soft-start; (7)logic-controlled, high-voltage switch with adjustable delay; (8)built-in power-up sequence; (9)input supply undervoltage lockout; (10)timer delay fault latch for all regulator outputs; (11)thermal-overload protection.The step-up DC-DC converter provides the regulated supply voltage for the panel source driver ICs. The converter is a high-frequency (600kHz/1.2MHz) currentmode regulator with an integrated 14V n-channel MOSFET that allows the use of ultra-small inductors and ceramic capacitors. It provides fast transient response to pulsed loads while achieving efficiencies over 85%.

The absolute maximum ratings of the MAX8739 can be summarized as:(1)operating temp:-40 to 85;(2)storage temperature range:-65 to +150;(3)lead temperature (soldering, 10s) :+300;(4)IN, CTL, FREQ, LDO to AGND:-0.3V to +6V;(5)LX to PGND:-0.3V to +14V;(6)LX switch maximum continuous RMS output current:1.6A.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.On the rising edge of the internal clock, the controller MAX8739 sets a flip-flop, turning on the n-channel MOSFET and applying the input voltage across the inductor. The current through the inductor ramps up linearly, storing energy in its magnetic field. Once the sum of the current- feedback signal and the slope compensation exceed the COMP voltage, the controller MAX8739 resets the flipflop and turns off the MOSFET. Since the inductor current is continuous, a transverse potential develops across the inductor that turns on the diode (D1). The voltage across the inductor then becomes the difference between the output voltage and the input voltage.