Electronic Design

LED Driver’s “In-situ” Temperature Compensation Engine Benefits Mobile Phones

The LDS8160 LED driver from Leadis Technology features the company’s proprietary LED-Sense temperature-compensation engine and its patent-pending PowerLite current regulator (see the figure). The former monitors the in-situ temperature on each LED and independently optimizes the LED current for best luminosity-versus-temperature performance. The latter ensures a low dropout (LDO) voltage on each LED channel—typically 25 mV across the full operating current range.

To minimize standby current, the LDS8160 also features an additional low-power standby mode, where the supply voltage of the device is switched to 1.8 V. The LDS8160 is controlled though a high-speed I2C interface. It targets mobile backlighting applications and supports up to six white LEDs or two RGB LEDs, with a maximum current of 25 mA per channel.

The company’s proprietary LED-Sense temperature compensation engine measures the temperature of each LED at the diode itself, rather than in the proximity of the LED. Leadis Technology claims this in-situ measurement doubles the accuracy of conventional methods and does not require extra sensor components on the board.

Every few seconds, the measured temperature is fed into the compensation engine, which adjusts the current on each LED channel to optimize luminosity and color saturation and to prevent system overheating. Sixteen I2C-programmable registers for each of three channel banks let users define the compensation curve as a function of the specific LED used in the design.

The LDS8160 offers multiple advantages for designers of portable applications. Battery life efficiency is increased with the PowerLite current regulator and the exclusion of boosting circuits that are not needed with most of today’s LEDs. The ultra-low-dropout PowerLite current regulator provides a transition threshold of 25 mV, allowing designers to use any LED with a VF lower than 3.4 V.

For improved dynamic brightness control, three 12-bit logarithmic pulse-width modulation (PWM) generators are integrated on chip. These generators send a dimming command through the I2C interface without having to keep “pulsing” a PWM bus, which improves the power consumption of the system, especially if frequent dimming is required.

The LDS8160 is offered in a 3- by 3-mm 16-pin thin quad flat no-lead (TQFN) package and in an ultra-small wafer-level chip-size package (WCSP) 3- by 4-ball grid package with 0.4-mm pitch.

Leadis Technology Inc.

www.leadis.com

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