TRIAC helps designers improve thermal management

7th September 2018

Enaie Azambuja

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Littelfuse has introduced six series of high-temperature sensitive, standard and alternistor TRIAC, designed for use as semiconductor switches in appliances and equipment powered by line AC voltages up to 220VRMS. Available in compact, surface-mount packages, these components are the industry’s first TRIAC with such a high maximum temperature that are available in ratings of 4A, 6A, and 8A.

This combination of space-saving packaging, high temperature capabilities and choice of current ratings makes them appropriate for IoT applications that require compact design but don’t involve continuous high currents such as smart doorbells, thermostats, ceiling fans/lights, door locks, etc.

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.

Typical applications for TRIAC include:

• 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 minimise 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. Sample requests may be placed through authorised Littelfuse distributors worldwide.