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Temp sensor IC enables efficient LED lighting

Posted: 19 Jan 2011 ?? ?Print Version ?Bookmark and Share

Keywords:LED lighting? pulse width modulation? temperature sensor IC?

Seiko Instruments Inc. (SII) launches the S-5855A Series of pulse width modulation (PWM) output temperature sensor IC for LED lighting designs. The S-5855A begins to decrease the duty ratio of PWM signal output when the temperature exceeds the specified value. This change in the duty ratio enables LED lighting circuits to avoid temperatures increasing above design limits, thus improving safety and efficiency while reducing total design cost.

The LED lighting and display backlights market has experienced rapid growth. Although LED lighting has strong efficiency advantages compared with incandescence, design consideration needs to be paid to LED heat management to avoid shortening lifetimes. Generally, this is implemented by performing thermal design to improve case heat dissipation, decreasing light intensity at high temperatures and stopping operation when the temperature rise exceeds the thermal design value (putting out the lights).

SII's output temperature sensor IC is optimized for use in LED lighting systems for PC laptops, tablets and other devices. It can also be used with any system requiring temperature control. The S-5855A is connected to the DIM pin of an LED driver IC to control the LED luminance, enhancing safety protection and boosting efficiency.

The S-5855A maintains 100 percent luminescence up to the specified temperature. Once the specified temperature is exceeded, the S-5855A decreases the PWM output duty ratio gradually along with an increasing temperature. This enables the LED luminance to diminish gradually. The S-5855A can also be connected to the DIM pin of the LED driver IC directly.

The S-5855A uses a very small SNT-4A package (1.2x 1.6x 0.5mm), enabling high density mounting. The standard SOT-23-5 package (2.9x 2.8x 1.3mm) is also available. The S-5855A features voltage operation of 1.65V to 5.5V and is suitable for battery-operated portable equipment.

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