The MAX8722C integrated backlight controller is optimized
to drive cold-cathode fluorescent lamps (CCFLs)
using a full-bridge resonant inverter architecture.
Resonant operation maximizes striking capability and
provides near-sinusoidal waveforms over the entire
input range to improve CCFL lifetime. The controller
operates over a wide input voltage range (4.6V to 28V)
with high power to light efficiency. The device also
includes safety features that effectively protect against
many single-point fault conditions including lamp-out
and short-circuit faults.
The MAX8722C achieves 10:1 dimming range by “chopping”
the lamp current on and off using a digital pulsewidth
modulation (DPWM) method. The DPWM frequency
can be accurately adjusted with a resistor or synchronized
to an external signal. The brightness is controlled
by an analog voltage on the CNTL pin. The device directly
drives the four external n-channel power MOSFETs of
the full-bridge inverter. An internal 5.4V linear regulator
powers the MOSFET drivers, the DPWM oscillator, and
most of the internal circuitry. The MAX8722C is available
in a low-cost, 24-pin QSOP package and operates over a
-40°C to +85°C temperature range.
Applications
Notebook Computer Displays
LCD Monitors
LCD TVs