The MAX1698 and MAX1698A are efficient drivers for white or color LEDs. They are ideal for large LED backlit displays in PDAs and laptop computers. Numerous benefits include greater simplicity, lower cost, higher efficiency, longer bulb life, and greater reliability when compared to fluorescent (CCFL) and electrolumines- cent (EL) lamps. The MAX1698/MAX1698A are switch-mode boost con- trollers in which LED current, rather than output voltage, is regulated The devices drive series-connected LEDs with a controlled current that is measured with a typically- ly 15Ω sense resistor, not an expensive fractional-ohm value. LED current control and dimming are accom- plished with an adjust input (ADJ). For larger light out- put, multiple LED banks can be connected in parallel with up to 5W total output power. The MAX1698A has a higher, and more accurately specified, CS current limit than the MAX1698 for higher- power applications of 5W or more. Both devices are supplied in a space-saving 10-pin µMAX package that occupies half the space of an 8-pin SO. An evaluation kit (MAX1698EVKIT) is available to speed designs.
The MAX1698 and MAX1698A are step‑up current regulators designed to drive white or color LEDs for backlit displays in PDAs, notebook PCs and other battery‑powered devices. They regulate LED current rather than voltage, using a sense resistor and an adjustable ADJ pin for brightness control. The devices are supplied in a compact 10‑pin UMAX package and support up to 5 W total output power.
Key features include over 90 % efficiency, lossless adjustable brightness, and the ability to connect multiple LED banks in parallel. The datasheet provides absolute maximum ratings, electrical characteristics, pin descriptions, typical operating curves, and design guidelines for inductors, capacitors, MOSFETs and layout.
| Supply Voltage | 2.7 V – 5.5 V |
|---|---|
| Maximum Output Power | up to 5 W |
| Efficiency | over 90 % |
| Operating Temperature Range | -40 °C to +85 °C |
The device can deliver up to 5 W of total output power.
Brightness is adjusted by applying a voltage to the ADJ pin, which changes the regulated LED current.
The regulator operates with over 90 % efficiency.