MAX17122

  _ MAX17122 19-4951; Rev 1; 11/09 EVAALVUAAILTAIOBNLEKIT Step-Up, Step-Down Regulator, Gate-On Charge Pump, and Boost-Buck Regulator for TV TFT LCD Display General Description The MAX17122 multiple-output power-supply IC generates all the supply rails for thin-film transistor (TFT) liquidcrystal 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 stepup regulator to power the TFT source drivers, and a temperature-compensated 36V internal-switch boostbuck 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. Highfrequency 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 gatedriver 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 inclu...