Driving nine LEDs on a power budget, says ams

An LED driver has been designed by ams which controls up to nine LEDs while saving power in LTE mobile devices because it operates independent of the baseband processor.

Typically used for indicator lighting, the AS3661 allows command-based programming of all light patterns.

Three independent program execution engines form three independently programmable LED banks which can be grouped based on their function. 

Each bank can contain from one to nine LED driver outputs; the AS3661 offers nine LED channels in total with up to 25mA per channel. A dedicated 12-bit PWM for each of the nine channels delivers absolutely smooth color transitions and enables the production of linear, logarithmic and ratiometric fading effects.

Instructions for the program execution engines are stored in the program memory. The total capacity of the program memory is 96 instructions and the user can allocate a memory of 1.5kbit as re-quired by the engines.

“Our AS3661 smartlight driver enables systems designers to offer users more eye-catching effects and functionality than ever before. This new product truly brings color into the life of portable devices,” said Ronald Tingl, senior marketing manager of opto-electronic products at ams.

The AS3661 smart LED driver has an I2C-compatible control interface with four pin-selectable addresses. The device also has a flexible General Purpose Output (GPO) which can be used as a digital control pin for other devices. The INT pin can be used to notify the central processor when a lighting sequence has ended.

The device also provides a trigger input interface which allows for synchronization between multiple devices.

The driver includes various power-saving features. Each channel operates on a dropout voltage of less than 50mV at 10mA powered by a high-efficiency 150mA charge pump with automatic switching between 1:1 and 1:1.5 mode.

A power save mode is automatically entered when LED outputs are not active, resulting in a low idle mode current of 10µA (typical).


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