The MAX8709B integrated backlight controller is
optimized to drive cold-cathode fluorescent lamps
(CCFLs) using a resonant full-bridge inverter architecture.
The 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 of 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 MAX8709B achieves 10:1 dimming range by “chopping”
the lamp current on and off using a digital pulse-width-modulation (DPWM) method. The minimum DPWM
duty cycle of the MAX8709B is 12.5%. The brightness is
controlled with a 2-wire SMBus™-compatible interface.
The device directly drives the four external N-channel
power MOSFETs of the full-bridge inverter. An internal
5.3V linear regulator powers the MOSFET drivers, the
DPWM oscillator, and most of the internal circuitry. The
MAX8709B is available in a space-saving 28-pin
thin QFN package and operates over a -40°C to +85°C
temperature range.
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