Seiko Instruments Inc. (SII) on Jan. 17 announced the S-5855A Series, a PWM (pulse width modulation) output temperature sensor IC for LED lightning designs. SII’s 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, improving safety and efficiency while reducing total design cost.
Recently the market for LED lighting and display backlights has experienced rapid growth. Although LED lighting has strong efficiency advantages compared to incandescence, design consideration needs to be paid to LED heat management to avoid shortening lifetimes. Generally this is implemented by (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.
Detailed information:
http://datasheet.sii-ic.com/en/temperature_sensor/S5855A_E.pdf
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