The MAX8751 cold-cathode-fluorescent lamp (CCFL)
inverter controller is designed to drive multiple CCFLs
using the fixed-frequency, full-bridge inverter topology.
The MAX8751 operates in resonant mode during striking
and switches over to constant-frequency operation after
all the lamps are lit. This unique feature ensures reliable
striking under all conditions and reduces the transformer
stress.
The MAX8751 can drive large power MOSFETs typically
used in applications where one power stage drives four
or more CCFL lamps in parallel. An internal 5.35V linear
regulator powers the MOSFET drivers and most of the
internal circuitry. The controller operates over a wide
input-voltage range (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 conditions.
The MAX8751 achieves a 10:1 dimming range by "chopping"
the lamp current on and off using the digital pulse-width
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 MAX8751 is capable of synchronizing and adjusting
the phase of the gate drivers and DPWM oscillator. These
features allow multiple MAX8751 ICs to be connected in a
daisy-chain configuration. The switching frequency and
DPWM frequency can be easily adjusted using external
resistors, or synchronized with system signals. If the controller
loses the external sync signals, it switches over to
the internal oscillators and keeps operating. Phase-shift
select pins PS1 and PS2 can be used to program up to
four different phase shifts, allowing up to five MAX8751s
to be used together.
The MAX8751 is available in a low-profile, 32-pin TQFN
package and operates over the -40°C to +85°C temperature
range.
Applications
- LCD Monitors
- LCD TVs
- Notebook Computers
