The MAX8729 cold-cathode-fluorescent lamp (CCFL)
inverter controller is designed to drive multiple CCFLs
using the half-bridge inverter consisting of two external
n-channel power MOSFETs. The half-bridge topology
minimizes the component count, while providing near
sinusoidal drive waveforms. The MAX8729 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 MAX8729 provides accurate lamp-current regulation
(±2.5%). The lamp current is adjustable with an external
resistor. The MAX8729 changes the brightness by turning
the CCFL on and off using a digital pulse-width modulation
(DPWM) method, while maintaining the lamp current
constant. The brightness can be adjusted with an analog
voltage on the CNTL pin, or with an external PWM signal.
The MAX8729 is capable of synchronizing and adjusting
the phase of the gate drivers and DPWM oscillator. These
features allow multiple MAX8729 ICs to be connected in a
daisy-chain configuration. The switching frequency and
DPWM frequency of the master IC 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 four different phase shifts, allowing up to five
MAX8729s to be used together.
The MAX8729 protects the inverter from lamp-out, secondary
overvoltage, and secondary short-circuit faults.
The MAX8729 can drive large-power MOSFETs typically
used in applications where one power stage drives four
or more CCFL tubes in parallel. An internal 5.35V linear
regulator powers the MOSFET drivers and most of the
internal circuitry. The MAX8729 is available in a low-cost,
28-pin QSOP package and operates over the -40°C to
+85°C extended temperature range.
* Some packages have variations, listed on the drawing. "PkgCode/Variation" tells which variation the product uses. Note that "+", "#", "-" in the part number suffix describes RoHS status. Package drawings may show a different suffix character.
Devices:
1-2 of 2
MAX8729
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TYPE PINS FOOTPRINT
DRAWING CODE/VAR *
Temp
RoHS/Lead-Free? Materials Analysis
MAX8729EEI
Active
QSOP;28 pin;61.9 mm²
Outline Drawing: 21-0055 (PDF)
Land Pattern: 90-0173 (PDF)
Use pkgcode/variation: E28-2*
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