The MAX1889 provides the three regulated output voltages
required for active matrix, thin-film transistor liquid
crystal displays (TFT LCDs). It combines a high-performance
step-up regulator with two linear-regulator controllers
and multiple levels of protection circuitry for a
complete power-supply system.
The main DC-DC converter is a high-frequency
(500kHz/1MHz), current-mode step-up regulator with
an integrated N-channel power MOSFET that allows the
use of ultra-small inductors and ceramic capacitors.
With its high closed-loop bandwidth performance, the
MAX1889 provides fast transient response to pulsed
loads while operating with efficiencies over 85%. The
positive and negative linear-regulator controllers postregulate
charge-pump outputs for TFT gate-on and
gate-off supplies.
The MAX1889 has a unique input switch control that
can replace the typical input fuse by disconnecting the
load from the input supply when a fault is detected.
The fault detector monitors all three regulated output
voltages and can monitor current from the input supply
as well. Additionally, the MAX1889 enters thermal shutdown
when its overtemperature threshold is reached.
The MAX1889 undervoltage lockout is set at 2.5V (max)
to allow the input supply to droop under pulsed load
conditions while avoiding any unexpected behavior
when its input voltage dips momentarily. Also, the builtin
soft-start and cycle-by-cycle current limiting prevent
input surge currents during power-up.
The MAX1889 is available in a 16-pin thin QFN package
with a maximum thickness of 0.8mm for ultra-thin
LCD panel design.
Applications
Notebook Computer Displays
LCD Monitors
Car Navigation Displays