The MAX17122 multiple-output power-supply IC generates all the supply rails for thin-film transistor (TFT) liquid-crystal display (LCD) TV panels. It can operate from 8V to 16.5V input voltages and is optimized for LCD TV panel applications running directly from 12V regulated supplies. It includes a 22V internal-switch step-down regulator for digital logic, a 22V internal switch step-up regulator to power the TFT source drivers, and a temperature-compensated 36V internal-switch boost-buck regulator that produces a negative output that can vary according to the temperature sensed by an external NTC thermistor. All three of these regulators feature high-efficiency and fixed-frequency operation. High-frequency operation allows the use of small inductors and capacitors, resulting in a compact solution.
The MAX17122 includes a positive charge-pump linear regulator controller that uses an external pnp bipolar junction transistor (BJT) to typically form a regulated charge-pump doubler to supply the LCD positive gate-driver supply voltage. A negative gate-driver supply is derived linearly between the boost-buck regulator's output and ground, using an external npn BJT connected to
ground and a small bypass capacitor.
Other features include an external-capacitor-timed, open-drain, power-good output that monitors the step-down regulator's feedback and a simple untimed output that monitors the positive charge-pump linear regulator's feedback. A high-voltage stress function is available for the step-up regulator output. The GATE output directly drives an external p-channel MOSFET to provide True Shutdown™ of the step-up output.
The MAX17122 is available in a 6mm x 6mm, 40-pin thin QFN package and operates over the -40°C to +85°C temperature range.
