Efficient, Reliable and Compact eFuse Optimized Server and Data Center Power Designs When designing server and data center power supplies, designers need to consider improving energy efficiency and power density while ensuring the highest possible safety and reliability. A series of challenges, such as the concern of unsecured work area (SOA), and functional safety such as diagnosis and response, and so on. ON Semiconductor offers a lineup of efficient, reliable and compact eFuse solutions, including a 3 V to 12 V power supply range and upcoming 24 V, 48 V eFuses, to help designers address these challenges. Built-in real-time diagnostics, precision control, and multiple protection features, these eFuses deliver fast response and outperform the competition in performance and reliability.
eFuse Introduction, Features and Target Applications

eFuse integrates over-current, over-temperature and over-voltage protection, provides current detection, fault reporting, output switch control, reverse current protection, short-to-ground protection, short-to-battery protection, resettable for any hot-swap application and needs to limit over-current system to prevent damage to connectors, PCB routing and downstream devices.
eFuse compares traditional fuse and PTC resettable fuse

There are usually blown fuses, positive temperature coefficient (PTC) resettable fuses, hot swap controllers, eFuse and other current limiting protection schemes. Taking a 600 W, 20 A DC power supply as an example, the current peak of the solution using the blown fuse and the PTC resettable fuse can be as high as 80 A and 58 A, respectively, while the current peak of the solution using the eFuse is only 7 A.

Blown fuses are disposable and must be replaced after a high current event blows. The PTC resettable fuse is in a low resistance state during normal operation. When a short circuit occurs, the PTC resettable fuse heats up and changes from a low resistance state to a high resistance state, thereby providing a protection function. When the fault is removed, the PTC resettable fuse cools down and reset to a low-impedance state. Different from blown fuses and PTC resettable fuses, eFuse does not limit the current based on heating, but measures the current. If the current exceeds the specified limit, the current is limited to a preset value, and then the internal switch is turned off when it overheats. . Compared with traditional fuses, eFuse has the following significant advantages:

Parameter Variation During Over Temperature Operation Minimal No Destruction After Fault Adjustable Current Limit Enable Pin Turns Device On or Off Current voltage clamp to prevent load from being affected by voltage spikes Advantages of resettable fuses.

Table 1: eFuse vs PPTC resettable fuse

eFuse vs. hot-swap controllers

Hot-swap controllers offer advanced features and diagnostics, can increase the current limit by using different FETs, have tight current tolerance, but are difficult to guarantee operation at SOA and more expensive. The eFuses are guaranteed to always operate within the SOA, provide real-time thermal feedback, increase the current limit by paralleling the eFuses, save board space, and provide a better price/performance ratio.

eFuses are easily paralleled to increase output current capability

In practical applications, the operating current of the system may be higher than the current load specified by the eFuse, and we can increase the output current capability by paralleling the eFuse. In the design, we connect the enable pin and fault pin of the eFuse in parallel. ON Semiconductor's eFuse has a unique three-state enable/fault pin, and a high level represents normal operation. A medium level represents thermal shutdown mode, and a low level represents complete output shutdown.

Figure: 12 V eFuse Parallel Demo

ON Semiconductor's Efficient, Reliable, and Compact eFuse Lineup

In the 3 V to 5 V power supply range, ON Semiconductor's eFuses mainly include NIS5135 , NIS5452 and will soon launch NIS2205, NIS2x5x, NIS3x5x, NIS6452, NIS6150, NIS6350, NIS800x, the on-resistance from 33 m 8486 ; to 200 mΩ, the current from 1 A to 5 A. Among them, NIS6452, NIS6150, NIS6350 integrated reverse current blocking (RCP) feature, NIS6150, NIS6350 also passed the automotive-grade AEQ-Q100 certification. It is worth mentioning that NIS6x50 also integrates a new feature IMON, by connecting a resistor between the IMON pin and GND to convert the IMON current into a ground reference voltage, thereby realizing current monitoring.
For 12V power supply, ON Semiconductor mainly provides NIS5020/NIS5021, NIS5820, NIS5232, NIS2x2x and will launch NIS5420, NIS2402 and NIS3220 soon, with on-resistance from 14 mΩ to 100 mΩ and current from 2.4 A to 12 A. Among them, NIS5020 has no IMON pin, but can measure the load current by detecting Rlim voltage, so as to achieve system-level enhancement, related application notes can be found in AND9685/D
Figure: NIS5020 measures load current by detecting Rlim voltage

Power input stages are often vulnerable to voltage spikes and transients during hot swapping, ON Semiconductor's eFuse integrates overvoltage protection that provides fast response and limits the output voltage, making it less susceptible to voltage transients. Some applications require delayed output turn-on after hot-insertion to stabilize the input voltage. See AND9672/D for related application notes.

Figure: 12 V eFuse hot-plug startup delay for system-level enhancement

In addition, ON Semiconductor will soon launch 24 V NIS6124 and 48 V high current eFuse, NIS6124 provides 40 V withstand voltage for 24 to 36 V, 48 V series features: high-side eFuse overcurrent shutdown, 48V application up to 80V peak input Voltage, DC capability over 120 A and extended current capability by adding MOSFETs, active magnetizing inrush current limiting for capacitive loads, V2 auto-retry function. The 48 V eFuse can be tested immediately, the PCB can be simplified or modified as needed, and it can be used as a reference design.


reliability test

ON Semiconductor's eFuses have been repeatedly tested for short-circuit reliability (AEC-Q100-012). Tests were performed at 25°C and -40°C to provide the highest thermal excursion and stress, and were run for 100,000 to 1,000,000 cycles with no functional issues and no change in on-resistance or other parameters. Compared with competitors, ON Semiconductor's eFuse has better surge performance.

Summarize

The safety and reliability of server and data center power supplies are critical. eFuse integrates over-current, over-temperature and over-voltage protection, and provides diagnostic and control functions. It has advantages over traditional fuses, PTC resettable fuses and hot-swap controllers, and is a cost-effective alternative. ON Semiconductor offers a lineup of efficient, reliable and compact eFuse solutions, including a 3 V to 12V power supply range and upcoming 24V and 48 V high-current eFuses with built-in real-time diagnostics, precision control and multiple protection features to ensure always-on SOA operation , Fast response, repeated short circuit reliability test, protect the circuit from high inrush current, voltage spikes and heat dissipation, performance and reliability are better than competitors, such as unique 3-state enable/fault pin , eFuses can be paralleled to enhance current capability, new IMON features enable output current monitoring, hot-plug startup delay for system-level enhancements, and more.