These new e-fuse offerings from Toshiba, Nexperia, and STMicroelectronics serve manifold applications: laptops, vehicles, datacenters, and beyond.In today’s round-up, we look at the latest electronic fuse (e-fuse) offerings from Toshiba, Nexperia, and STMicroelectronics. E-fuses monitor a power line for current, voltage, and other covered conditions.
Unlike their conventional namesake, e-fuses are resettable for use over many events. They are electronically controlled, enabling protection from multiple failure vectors and giving them advantages over circuit breakers. A typical e-fuse contains internal control circuitry and uses an N-channel MOSFET as the voltage pass or blocking switch. zThe MOSFET can be integrated, as is the case for products in this roundup, or external. If the covered conditions are exceeded, the electronics will shut off the MOSFET.
Toshiba Unveils Compact, High-Voltage E-Fuses
Toshiba recently released a new line of resettable e-fuse integrated circuits, the TCKE9 series (datasheet linked). The new e-fuse chip line protects power supply lines from overcurrent and overvoltage conditions. The chips also feature overtemperature and short-circuit protection. Standard fuses and circuit breakers typically protect from just overcurrent, leaving other faults like overvoltage clamping, current-induced thermal protection, and short-circuit protection to external circuitry with multiple discrete components. By combining such flexibility in one chip, designers can simplify the overall circuit and reduce parts count.
Block diagram of the TCKE9 series. Image used courtesy of Toshiba
The first two components in the product line, the TCKE903NL and TCKE905ANA, are shipping now, with more family members to follow. When complete, the product line will offer power supply volt ratings of 3.3 V, 5 V, 12 V, and 20 V. The integrated MOSFET has an RDS(on) of 34 mΩ. The e-fuses have adjustable current set values with a range from 0.5 A to 4.0 A. The components will come in two breaker varieties: auto retry and latching. In an auto-retry setting, the e-fuse will self-reset after certain conditions are met. In a latching configuration, the e-fuse requires an external reset signal.
Nexperia Boasts Current Limiting Accuracy in New E-Fuses
Nexperia announced a new addition to its e-fuse product line with a set of high-current, high-accuracy fuses. The NPS3102A and NPS3102B (datasheet linked) resettable fuses operate at up to 21 V and a max current trip value of 13.5 A. They protect downstream loads from a number of fault conditions, including overcurrent, overvoltage, excess inrush current, and load faults. The chips have a 20 μs over-current shut-off and 2 μs response time for a short-circuit fault.
Block diagram of the NPS3102A and NPS3102B. Image used courtesy of Nexperia
The current limit can be adjusted from 2 A to 13.5 A via an external resistor. The e-fuse can also operate in a current-limiting mode, where the MOSFET is partially shut off to only pass through current within the specific limit. If the downstream device continues to draw excess current, the device will trigger and shut power off. The current limit capability allows the chip to supply power to devices that have strict current specifications or devices that consume as much power as it can pull out of a supply.
While the device’s fusing control is internal, it can connect to an external microcontroller via an enable/fault pin. The bidirectional pin indicates a fault condition and powers the device off. The “A” model requires a manual reset after a fault condition, while the “B” model contains auto-reset attempt circuitry. The passthrough MOSFET has an RDS(on) of just 17 mΩ.
STMicroelectronics Releases Smart Automotive Circuit Breaker
ST shared news about its new intelligent automotive circuit breaker e-fuse built into a high-side MOSFET driver chip. The VNF9Q20F (datasheet linked) is a quad-channel monolithic IC with internal MOSFETs. The chip can be used as a quad-high-side driver with integrated e-fuse or for e-fused power on/off control switching in systems that require multiple power buses. The chip includes ST's proprietary STI2Fuse (current squared through time-to-fuse) circuitry to deliver a response time of 100 µs or less to a fault condition. It can operate in a latch off with manual reset or programmable auto-retry timed mode.
Block diagram of the VNF9Q20F. Image used courtesy of STMicroelectronics
ST designed the VNF9Q20F for harsh environments, like automotive applications. The four-channel device has four independent internal N-channel MOSFET switches for power control. Each can fault or be controlled independently of the others. The internal MOSFETs allow the four outputs to directly drive resistive or inductive loads that connect to ground. It contains four independent pulse width modulation (PWM) generators—one for each of the four output channels.
In addition to the e-fuse functionality with 64 programmable current limit values, the chip prevents inrush current issues and has advanced diagnostic capabilities. It communicates with a host microcontroller over the SPI bus and includes a 10-bit analog-to-digital converter (ADC) and fault registers. The SPI bus is used for configuration, status reading, and condition monitoring. The chip has a failsafe mode that preserves operational status in the event of a system failure or malfunction.
