Date: 19/01/2011

LED lighting specific temperature sensor chip from Seiko

Seiko Instruments Inc. has announced the S-5855A Series, a PWM (pulse width modulation) output temperature sensor IC for LED lightning designs. SII's S-5855A adjusts the duty ratio of PWM signal output when the temperature exceeds the specified value to avoid temperatures increasing above design limits, improving safety and efficiency while reducing total design cost.

LED heat management is done in three ways they are (1) performing thermal design to improve case heat dissipation, (2) decreasing light intensity at high temperatures and (3) stopping operation when the temperature rise exceeds the thermal design value (putting out the lights).

SII's S-5855A 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% 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. Also, since the S-5855A can be connected to the DIM pin of the LED driver IC directly, it simplifies and improves design safety as well as efficiency.

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

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