Smartphone LCD backlight LED drivers tout highest efficiency, smallest PCB area

Smart phones are being operated as power-hungry mini computers that use large displays with significant power requirements. But at the same time designers are challenged to extend the battery capacity of the smart phones while shrinking their overall size.

austriamicrosystems believes it has resolved that issue with a pair of LED drivers that it claims enables the industry’s best application efficiency at a peak level of 90%, including the DC-DC converter and current sources.

With a PCB footprint of only 11.5 mm², and just four external components required, the AS3674 and AS3940 are well suited for smart phones and other mobile devices.

The AS3674 is a highly efficient 2 MHz DC-DC switch mode step-up converter controlling 5 current sources with each driving 2 LEDs in series. For added flexibility, the current for the LED channels can be set by an external resistor with a maximum of 25 mA per channel. The AS3490 incorporates the same functionality as the AS3674 but addresses only three LED channels. 

A soft startup feature allows the AS3674 to be easily integrated into noise sensitive RF systems. The AS3674 is controlled by two enable inputs which can also serve as PWM inputs between 100 Hz and 800 Hz with 1:2000 dimming ratio. The 2 LED per channel configuration combined with the 2 MHz operating frequency of the converter allow the use of tiny external components such as a 4.7 µH coil and results in very high efficiency, up to 6% higher than the closest competitor.

The AS3674 operates from a 2.5 to 5.5 V power supply and includes a number of safety features such as under-voltage lockout, overcurrent and over-temperature protection and LED testing. Both the AS3674 and AS3490 are housed in space saving 12-ball WL-CSP package (1.7 x 1.4 x 0.5 mm, 0.4 mm pitch). 

Availability: Samples of the AS3674 and AS3490 are available now.  

Datasheets: AS3674 and AS3490