8-String White LED Driver with SMBus for LCD Panel Applications

Active: In Production.

The MAX17061A is a high-efficiency driver for white light-emitting diodes (LEDs). It is designed for large liquid-crystal displays (LCDs) that employ an array of LEDs as the light source. An internal switch current-mode step-up controller drives the LED array, which can be configured for up to eight strings in parallel and 10 LEDs per string. Each string is terminated with ballast that achieves ±1.5% current-regulation accuracy between strings, ensuring even LED brightness. The MAX17061A has a wide input-voltage range from 7.5V to 26V, and provides a fixed 25mA or adjustable 15mA to 30mA full-scale LED current.

The MAX17061A internally generates a DPWM signal for accurate WLED dimming control. The DPWM frequency is resistor programmable, while DPWM duty cycle is controlled directly from an external PWM signal or through a control word through the MAX17061A's SMBus™ interface. This DPWM control provides a dimming range with 8-bit resolution and supports Intel display-power-saving technology (DPST) to maximize battery life.

The MAX17061A has multiple features to protect the controller from fault conditions. Separate feedback loops limit the output voltage under any circumstance, ensuring safe operation. Once an open string is detected, the string is disabled while other strings operate normally. The MAX17061A also features short LED detection. The shorted strings are also disabled after a 2ms fault blanking interval. The controller features cycle-by-cycle current limit to provide stable operation and soft-start capability. If the MAX17061A is in current-limit condition, the step-up converter is latched off after an internal timer expires. A thermal-shutdown circuit provides another level of protection.

The MAX17061A's step-up controller features an internal 150mΩ (typ), 45V (max) power MOSFET with local current-sense amplifier for accurate cycle-by-cycle current limit. This architecture greatly simplifies the external circuitry and saves PCB space. Low-feedback voltage at each LED string 625mV (typ) at 25mA LED current helps reduce power loss and improve efficiency. The MAX17061A features selectable switching frequency (500kHz, 750kHz, or 1MHz), which enables a wide variety of applications that can trade off component size for operating frequency.

The MAX17061A is available in a thermally enhanced 28-pin, 4mm x 4mm Thin QFN package.

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