Industry White Papers

Littelfuse - 5 New Technologies for Building Automation

September 01, 2020 by Mouser Electronics

Building automation is a rapidly expanding area of electronic design. This article goes over five new technologies pushing this technology forward from the component level.

Every second, 127 more devices connect to the internet. The introduction of the iPhone in 2007 catapulted us into the era of near-universal connectivity. With companies preparing to spend over one trillion (USD) in the Internet of Things (IoT) in the next three years, it is easy to see that the ability to connect pieces of our lives wholly depends on the reliability of the equipment and infrastructure that links devices together. 

Previous unrelated systems such as smoke detectors and smart- home hubs share functionality with GFCI/AFCI, USB, and IoT outlets. Although some smart functionality (smoke detectors) is more critical than others (smart blinds), soon, all of our devices will be connected. This interdependency places higher importance on reliability for both the internet source and infrastructure, linking the devices to it. 

An increasingly connected world requires new, innovative solutions for power reliability, control, and sensing. This paper reviews five of the enabling technology opportunities for the IoT and the product solutions that bring them to life. 


High-Peak Surge Current Rating

AC line voltage (130VAC and 625VAC) surges come in various forms and scales. Lightning is one of the most common severe sources of rapid voltage increase and can cause immediate failure of electronic devices adjacent to the strike point. Smaller-magnitude surges, such as cyclic increases or decreases (or full on/off) in voltage from dimmer switches, fans, or thermostat settings, result in a slower performance erosion of the device. These surges still cause the devices to fail; it just happens more gradually over a longer time. 

External factors, such as variation in the grid power consistency or swings in demand, can also cause surges. The proximity of circuits to each other could lead to secondary surge failures because of an internal or external event to a primary circuit. 


Figure 1. UltraMOV 14 mm Varistors (Source: Mouser Electronics)


The Littelfuse UltraMOV varistor handles high-peak surge currents up to 10 kA and operating temperatures up to 125°C. It is rated up to 85°C ambient temperature without derating and is UL-recognized and TUV- certified to 800V isolation. In addition to protecting against line surges, engineers designed the UltraMOV for LED lighting, AC power taps and meters, and uninterruptable power supply applications. It can withstand surges from lightning and inductive load and capacitor bank switching.


Excessive Current Inrush at Startup

Similar to surges, extreme current inrush during startup leads to overheating. The heat must be removed either before the current reaches the component or removed at a rate high enough to avoid exceeding the rated temperature. The transient response of the system startup creates a rapid flow of current. This event can lead to component failure or even electrical fires without inline protection of the component. 

Assuming the cooling strategy is constant, the only feasible control remaining is a Silicon Controlled Rectifier (SCR). The SCR regulates the flow of current like a switch, blocking or allowing current to reach the downstream components. 


Figure 2. SJ SCR Switching Thyristors (Source: Mouser Electronics)


The Littelfuse SJ Series SCR Switching Thyristor addresses the overheat concern from a current inrush by offering a wide operating range. The SJ series has a high junction temperature of 150°C, up to 600V blocking voltage, and is rated at 4A to 40A. The SJ has smaller heat sinks than traditional SCRs, limiting the circuit temperature by minimizing conductive heat gain. 

Engineers select this series of SCR for converters/rectifiers, capacitive discharge systems, LED lighting, small-motor applications such as gasoline engines and generators, and in vehicular applications such as motorcycles and ATV. 


Low-Load LED Performance Consistency

LEDs are more challenging to dim than traditional lights. The failure mode (flickering) results from the inconsistent current because of insufficient carrying current. The significant efficiency benefit of LEDs over incandescent bulbs is because of LEDs requiring substantially less current at a comparable lighting condition. Pairing the LED with a traditional Triac dimmer cuts the current flow below the level the LED needs to provide consistent output, leading to flickering. 

LEDs require special Triacs that perform best at their low-load current profiles. With design points centered at lower amperage ranges, LED Triacs significantly decrease the probability of flickering with dimming operating conditions. 


Figure 3. Thyristor Triacs for LED Dimmer Applications (Source: Mouser Electronics)


Designed for a 6mA maximum holding current, the Littelfuse Thyristor Triac for LED dimming provides the user full control of output light without the risk of flickering over the range of LED operating points. It has a junction temperature rated at 110°C, minimizing the need for heat sinking, and provides safe operation at LED operating points with a di/dt performance of 70A/μs. 

In addition to LED dimming, engineers use the LED-capable Triac for AC switching and phase control in heating and lighting use cases, and in motor-speed control applications such as power tools, AC solid-state switches, and low-current motors for the home.


Reliable Overload Fuse Capability

The influx of connected components and on/off demand cycles creates many challenging conditions for fuses. While all the traditional household components such as the air conditioner and refrigerator consume power, increasing numbers of new smart devices compete for electric bandwidth. 

To address that competition, engineers use time-delay fuses. These components withstand two to three times the electrical current load of traditional fuses, allowing an overload for a short amount of time to reduce the chance of tripping a circuit breaker.


Figure 4. 473 Series - PICO® II Slo-Blo Subminiature Axial Leaded Fuse (Source: Littelfuse)


The Littelfuse 473 series time-delay fuse provides overload protection with the reliability that PICO fuses have always delivered. These fuses are small and operate at currents between 0.375A to 7A. The 473 series operates in a temperature range of -60°C to 125°C with low- temperature derating. 

The 473 Slo-Blo® time-delay fuse is used in LCD monitors and flat-panel TV applications as well as lighting systems and medical and industrial equipment. 


Low-Resistance Power Switching

Moving between power solutions on demand is a cornerstone for the IoT, especially with current infrastructure and technology levels that lag behind the lightning-fast pace of technology innovation. The resistance difference between the “on” and “off” sources creates resistance losses as the power is transferred from one source to another. The switch should maintain as low an ON resistance as possible while reducing package inductance to the degree possible.


Figure 5. X2-Class Power MOSFETs with HiPerFETTM (Source: Mouser Electronics)


The Littelfuse X2-Class provides ultra-low resistance with low-package inductance. It also operates at high-power density and high efficiency for maximum performance. The spatial efficiency of the switch allows ease of mounting and footprint space in a system. The X2-Class has fast response time with a lower heat signature than conventional switches and a dV/dt rating corresponding to a low ruggedness of power.

These switches are used in a wide variety of applications, ranging from EV battery chargers to renewable energy converters, and power factor correction circuits and robotics control. 

A critical feature to meet the electrical demand requirements of IoT is fast MOSFET switching. A high-and low-side gate driver promotes low- resistance switching.


Figure 6. IX4340 MOSFET Drivers (Source: Mouser Electronics)


The Littelfuse IX4340 drivers are a dual, high-current, low-side gate driver. Each of the drivers’ two outputs can source and sink 5A peak current and is rated to 20V maximum voltage (5V-20V range). The drivers have an extended operating temperature range between -40°C and 125°C and have fast propagation delays (16ns avg.) and rise and fall times (7ns). 

Applications that benefit from the 4340 drivers are power inverters, switch-mode power supply, DC-DC converter, and motor controller.


Industry Standards

Maintaining standards compliance is critical to successful product launches for IoT-ready outlets. These protection solutions help meet the industry safety and ESD standards required by IoT-capable outlets. The standards these products address include:



  • Lighting Dimmer: UL 1472, IEC
  • GFCI/AFCI: UL 943 (GFCI), IEC 61008 Series (RCD), UL 1699 (AFCI), IEC 62606
  • Smart Outlet: UL 231 
  • USB Receptable: UL 498

Electrostatic Discharge (ESD)

  • Electrostatis Discharge: IEC 61000-4-2 
  • Electical Fast Transient: IEC 61000-4-4 
  • Surge Immunity: IEC 61000-4-5 



The IoT is driving innovation by enabling technology for smart homes, connected appliances, increased speed and power management of USB 3.0, and improved LED compatibility. The infrastructure must address several opportunities to prepare for the high number of connected devices: 

  • High-peak surge current 
  • Excessive current inrush 
  • Low-load LED performance consistency 
  • Reliable overload fuse performance

Many of the design considerations speak to common occurrences that have plagued the electronics industry for years. But as these new devices increase in value, transitioning from novelty to utility, engineers must overcome these design consideration to deliver consistent, reliable power to the end uses. Selecting the appropriate power and reliability controlling solution ensures that the application is limited only by the imagination of the inventor, not the reliability of power delivered to the smart technology. 


Littelfuse is a global leader with a broad product portfolio of leading technologies in circuit protection, power control, and sensing. With application expertise and product design guidelines, we help you determine the best component for your application. We have full testing capabilities and provide assistance and local product support to ensure you select the best product for the application. Littelfuse fabricates components in high-volume manufacturing facilities and has expertise in UL and IEC standards.