MAX8784

The MAX8784 generates supply rails for the thin-film transistor (TFT) liquid-crystal display (LCD) panels in TVs and monitors. MAX8784 includes a step-up regulator, a regulated positive and a negative charge-pump, three high-current operational amplifiers, and Dual Mode™, logic-controlled,high-voltage switch control block.

Features of the MAX8784 are:(1)fast transient response to pulsed load; (2)built-in 18V, 4A, 0.11 n-channel power; (3)MOSFET with lossless current sensing; (4)cycle-by-cycle current-limit comparator; (5)90% efficiency (5V In to 15V out); (6)1.2MHz switching frequency; (7)regulated charge-pump tripler with integrated; (8)diodes for TFT gate-on supply; (9)regulated charge pump for TFT gate-off supply; (10)undervoltage and thermal protection; (11)4V to 5.5V input operating range.The three operational amplifiers drive the LCD backplane and the gamma-correction-divider string. Each operational amplifier has a fast slew rate (45V/s), a wide bandwidth (20MHz), and a high-output short-circuit current (200mA). Each op amp has rail-to-rail input and rail-to-rail output operation.

The absolute maximum ratings of the MAX8784 can be summarized as:(1)operating temp:-40 to 85;(2)storage temperature range:-65 to +160;(3)junction temperature range:150;(4)SUP to AGND:-0.3V to +22V;(5)DRN to GON:-30V to +30V;(6)RMS VCC current:50mA.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 section of this specification is not implied.Exposure to absolute maximum rating conditions for extended periods may affect device reliability.The step-up regulator MAX8784 achieves soft-start by linearly ramping up its internal current limit. The soft-start terminates when the output reaches regulation or the full current limit has been reached. The current limit rises from zero to the full current limit in approximately 3ms.The MAX8784 monitors FB for undervoltage conditions.If the voltage is continuously below 80% of the nominal regulation point for approximately 55ms, the MAX8784 sets the fault latch, shutting down all outputs except the reference and the operational amplifier.