MAX8722C

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.

Features of the MAX8722C are:(1)wide input voltage range (4.6V to 28V); (2)input-voltage feed-forward for excellent line rejection; (3)accurate dimming control with analog interface; (4)10:1 dimming range; (5)adjustable accurate DPWM frequency with sync function; (6)adjustable lamp current rise and fall time; (7)secondary voltage limit reduces transformer stress; (8)lamp-out protection with adjustable timeout; (9)secondary overcurrent protection with adjustable timeout; (10)low-cost, 24-Pin QSOP package.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 absolute maximum ratings of the MAX8722C can be summarized as:(1)PGND to AGND:-0.3V to +0.3V;(2)storage temperature range:-65 to +150;(3)operating temperature range:-40 to +85;(4)junction temperature:+150;(5)continuous power dissipation:761.9mW.Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied.Exposure to absolute maximum rating conditions for extended periods may affect device reliability.Theoretically, the output voltage of the resonant converter will increase until the lamp is ionized or until it reaches the IC's secondary voltage limit, without regard to the transformer turns ratio or the input voltage level. Once the lamp is ionized, the equivalent load resistance decreases rapidly and the operating point moves toward the series resonant peak.While in series resonant operation, the inverter behaves like a current source.