The MAX749 is a negative LCD-bias contrast voltage generator from Maxim Integrated that supports 2V to 6V input voltages. The full-scale output voltage can be scaled to -100V or greater, and is digitally adjustable in 64 equal steps by an internal digital-to-analog converter (DAC). The output voltage can also be adjusted using a PWM signal or a potentiometer. The MAX749 has a low static current (maximum 60µA) and a shutdown mode of only 15µA. It supports external P-channel MOSFET or PNP transistor driving, and is used in notebook computers, laptop computers, palmtop computers, personal digital assistants, communicating computers and portable data-collection terminals.
The MAX749 is a negative-output inverting power controller that generates LCD‑bias voltages from a 2 V to 6 V input. It provides a digitally adjustable output ranging up to –100 V, using an internal 64‑step DAC or external PWM, potentiometer, or resistor control.
The device is intended for notebook, laptop, palmtop, PDA, and other portable computer applications. It features ultra‑low quiescent current (60 pA typical, 600 pA max), a shutdown current of 15 pA, and a high switching frequency up to 500 kHz, allowing small external components and high efficiency.
| Input Voltage Range | 2 V to 6 V |
|---|---|
| Quiescent Current | 60 pA typical, 600 pA max |
| Shutdown Current | 15 pA |
| Switching Frequency | 100 kHz to 500 kHz |
| DAC Resolution | 64 equal steps |
The MAX749 operates with an input voltage from 2 V to 6 V.
The device draws a typical quiescent current of 60 pA (up to 600 pA max).
The internal DAC provides 64 equal steps for voltage adjustment.
In shutdown mode the MAX749 draws only 15 pA.