Since Edward V. Sundt invented the first small, fast-acting protective fuse to prevent sensitive test meters from burning out and founded the company in 1927, Littelfuse has become the world leader in circuit protection.
Littelfuse expertise encompasses many fields, including Consumer Electronics; Telecom; Medical Equipment; Lighting; TVSS and Power Supplies; Commercial & Recreational Vehicles; Industrial Equipment; and much more.
But there's a lot more to Littelfuse than fuses. They've expanded their expertise into sensors, including reed sensors, Hall Effect sensors, and magnetic actuators. And they offer a range of power control products including thyristors, generator ground-fault relays, IGBT modules and battery management modules.
Read on to find out how Littelfuse can Protect, Sense, and Control practically any power application.
Protect
Since its founding, Littelfuse has gone on to become the standard-bearer of the circuit protection industry. In the 1960's they developed mission-critical sub-miniature fuses for NASA's space program; in automotive, Littelfuse introduced the first centralized under-dash fuse block, the first blade fuses, and were the first circuit protection manufacturer to receive QS 9000 certification.
In addition to fuses, protection products include TVS diode arrays, positive temperature coefficient (PTC) devices, varistors, TVS diodes, protection thyristor (SIDACtor® protection thyristor), gas discharge tubes (GDTs), ESD suppressors, and surge protection modules (SPDs).
Littelfuse protection devices are used in hundreds of automotive applications including powertrain, lighting, instrument panels, and Li-Ion and NiMH batteries for electric vehicles. Their Auto-Grade ultralow capacitance diode arrays and - MLVs are well suited for high-speed and standard buses including USB, BroadReach, HDMI, and RF (Bluetooth, WiFi, GPS) as well as LINand CAN buses. Littelfuse products also appear in emerging systems such as night vision, and vehicle-to-vehicle (V2V) communications. Outside of automotive, Littelfuse is the leader in protection for telecom, wearables, IoT, medical, and many other industries.
Figure 1, for instance, shows a protection scheme for a 1000Base-T Ethernet installation which must withstand a peak current of over 36A per wire, as required in specifications from Standards bodies like GR1089 and ITU. The circuit includes four fuses, two SIDACtor® protection thyristors, and one TVS diode array.
Figure 1: A 1000Base-T circuit requires multiple levels of protection (Source: Littelfuse)
Sense
Littelfuse sensors detect and control position, proximity, level and speed in a wide range of automotive, consumer, and industrial applications. Their sensor product line includes reed switches, sensors, and relays; Hall Effect sensors; and magnetic actuators.
Figure 2: Littelfuse sensors include reed relays, reed switches, Hall Effect Sensors, as well as bare and packaged magnetic actuators.
A reed switch consists of two or three thin ferromagnetic metal blades called reeds. These reeds are coated with precious metals at their tips, and spaced a small distance apart. These are hermetically sealed within a glass tube filled with inert gas. The switch is actuated when a magnetic field is applied. A reed relay uses a coil to actuate the switch, while an encapsulated reed sensor package is usually actuated with a permanent magnet and is very effective as a position or proximity sensor.
Littelfuse also encapsulates the Hall Effect IC into various sensor package designs. Both digital and analog voltage output options are available, and also activated by a permanent magnet actuator. A Hall Effect sensor has a high resolution output and is very effective for speed sensing, rotary analog output sensing, and can be programmable when very precision sensing is required.
These families of magnetically actuated technologies are considered non-contact devices and have a long switching lifetime. The devices are very reliable, operate within many varying environments over a wide temperature range and are stable within high levels of mechanical stress.
These products are highly reliable and effective switching devices used in many applications including exercise equipment, water or gas metering, large and small appliances, HVAC, security, and automotive.
Figure 3: Block diagram of the 55075 stainless steel Hall Effect sensor (Source: Littelfuse)
Hall Effect sensors are offered in a variety of packages. The 55075 sensor in Figure 3, for example, is a stainless steel barrel sensor optimized for wheel, transmission and camshaft speed sensing in industrial, commercial, and automotive applications. It contains an on-chip 10-bit analog to digital converter (ADC) and can measure up to 15ksps. Many other packaging and performance options are available.
Sensor Application: Washing Machine
Figure 4: A washing machine design requires several different sensor technologies. (Source: Littelfuse)
Washing machines use a variety of sensors to ensure proper, safe, and energy-efficient operation. Figure 4 shows how Littelfuse sensors can help:
Lid/Door Position Sensing: For top or front loading washing machines, a reed sensor is mounted to the frame, hidden behind the machine’s outer exterior, and is activated by a magnet attached to the lid to indicate lid closure. The washing machine microcontroller can then allow drum rotation to begin.
Water Level Sensing: A PCB containing several reed switches and resistors spaced at approximately 10mm and used in conjunction with a magnet embedded in a float can measure the water depth in the tub. As the water level changes, the magnet moves up and down and activates the appropriate reed switch. The microcontroller monitors the water depth and controls this according to the depth required.
Dial Position Sensing: In dial positioning, a rotary Hall Effect sensor is mounted behind the panel while a magnet is attached to the dial. As the operator adjusts the dial angle the Hall detects the magnetic field angle and converts this to a voltage or pulse wave output that is precisely proportional to the proper angle setting.
Drum Speed Sensing: A Hall Effect speed sensor mounted to the fixed frame detects the speed of the multi-pole ring magnet mounted on the motor shaft to send speed information to the main microcontroller.
Control
To round out their protection offerings, Littelfuse has a range of control solutions as well. These include power thyristors such as Triacs up 1000V/40A, Quadracs up to 600V/12A, and SCRs up to 1000V/70A capability; Silicon and SiC Schottky diodes, Ultrafast Rectifier Diodes and IGBT modules. Through their partner Arrow, there are over 500 products in these categories.
The HQ6025xH5, for example, is a 25 Amp bi-directional Alternistor Triac. It is designed for AC switching and phase control applications requiring a higher temperature environment, such as the tankless water heater application example below. It features an RMS on-state current IT(RMS) of 25A and operates up to a maximum junction temperature of 150 ºC.
In IGBT modules, a representative device is the MG1275, which is intended for motor control and inverter applications. This IGBT operates up to a collector-emitter voltage (VCES) of 1200V with an average forward current (IF(AV)) of 75A. Figure 5 shows the internal block diagram of this device, which contains all of the power components necessary for an AC motor drive, including freewheeling reverse recovery diodes.
Figure 5: MG1275 Block Diagram (Source: Littelfuse)
In addition to power semiconductors, Littelfuse has modules for:
- Protection Relays
- Generator Controls & Monitoring
- Battery Management
- Heavy Duty Switching
They also design custom-engineered electrical equipment for a wide range of power applications.
A Single-Source Solution Example
A tankless water heater design provides a good example of an end-to-end protection solution. Tankless water heaters are becoming increasingly popular due to their ability to provide hot water on demand. They can also provide long-term energy savings since energy is used only when hot water is needed.
As shown in Figure 6, Littelfuse devices are used to:
- Indicate water flow with a reed switch or measure the amount of water flow with a reed or Hall Effect sensor.
- Control AC power to the heater with a triac from the HQ6025 family
- Provide AC protection with TMOV® or UltraMOV® series varistors
Provide DC protection for the touch screen or display panel with an SP1001 or SP1003 diode array or multilayer varistor from the MLA or MLE families.
Figure 6: the control panel for a tankless water heater showing the main components and Littelfuse protection components in green. (Source: Littelfuse)
Conclusion: Expertise Applied. Answer Delivered.
Expanding far beyond their initial base, Littelfuse now has broad-based expertise as a power control, sensing, distribution & protection products. Through a combination of product development and strategic acquisitions over many years, they now have the capability to offer complete power solutions in their selected markets.