High-temperature TRIAC For IoT and Home Automation


Littelfuse’s new TRIACs support operating junction temperature up to 150°C, easing thermal management

TRIAC thyristors are often used in AC circuits, motor speed controls, light dimmers, pressure-control systems and other electronic components. Littelfuse now offers designers six  new series of high-temperature sensitive, standard and alternistor TRIACs, designed for use as semiconductor switches in appliances and equipment powered by line AC voltages up to 220VRMS. The components are suitable for 24 VAC control, 110 VAC, AC solenoid/valve control, AC heating control and AC motor control applications.

These components are claimed as the first with such a high maximum temperature of up to 150°Cthat are available in ratings of 4A, 6A, and 8A. They are available in compact, surface-mount packages.


The combination of space-saving packaging, high-temperature capabilities and choice of current ratings, which make them well-suited for Internet of Things (IoT) applications that require compact design but don’t involve continuous high currents such as smart doorbells, thermostats, ceiling fans/lights, door locks, etc., according to Littelfuse.

The sensitive-type components guarantee low current gate control in Quadrants I and IV to interface directly with digital control circuitry. Standard-type components normally operate in Quadrants I and III and are triggered from the AC line. Alternistor-type components only operate in Quadrants I, II, and III, are triggered from the AC line, and are used in circuits requiring high dv/dt capability.

With a maximum junction temperature of 150 °C, these components help circuit designers facing thermal management issues due to limited or no heat sinking by providing a larger thermal design margin. Their high surge capabilities simplify handling cold in-rush currents in heater or motor control applications, Littelfuse noted.

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Typical applications for new TRIACs

  • 24VAC control such as smart doorbells, thermostats, sprinkler timers, door locks, etc.
  • 110VAC control such as smart ceiling lights/fans, LED flood lights, etc.
  • AC solenoid/valve control
  • AC heating control and AC motor control

“The combination of the robust clip-attach assembly design and the maximum operating junction temperature ensures the high surge capability needed to withstand short-duration overload conditions,” said Koichiro Yoshimoto, Business Development Manager, Semiconductor Business Unit at Littelfuse. “By offering a choice of current ratings in small, surface-mount packages, these components allow designers to minimize board sizes for low power applications such as LED lighting, solenoid drives and motor drives.


High-Temperature Sensitive, Standard and Alternistor TRIAC are available in TO-251 (VPAK) or TO-252 (DPAK) packages in tube pack (75 per tube) in quantities of 750 or in embossed carriers in quantities of 2,500.

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