Efficient, reliable and compact eFuse optimized server and data center power supply design

When designing server and data center power supplies, designers need to consider not only improving energy efficiency and power density, but also ensuring the highest possible safety and reliability, which brings a series of challenges, such as the concern of no safe operating area (SOA) , And functional safety such as diagnosis and response, etc. ON semiconductor provides an efficient, reliable and compact eFuse solution lineup, including a 3 V to 12 V power supply range and the upcoming 24 V, 48 V eFuse to help designers solve these challenges. These eFuses have built-in real-time diagnostic functions, precise control and multiple protection features, fast response, performance and reliability better than competitors.

Efficient, reliable and compact eFuse optimized server and data center power supply design

When designing server and data center power supplies, designers need to consider not only improving energy efficiency and power density, but also ensuring the highest possible safety and reliability, which brings a series of challenges, such as the concern of no safe operating area (SOA) , And functional safety such as diagnosis and response, etc. ON Semiconductor provides an efficient, reliable and compact eFuse solution lineup, including a 3 V to 12 V power supply range and the upcoming 24 V, 48 V eFuse to help designers solve these challenges. These eFuses have built-in real-time diagnostic functions, precise control and multiple protection features, fast response, performance and reliability better than competitors.

Introduction, features and target applications of eFuse

eFuse integrates over-current, over-heat and over-voltage protection, provides current detection, fault reporting, output switch control, reverse current protection, ground short-circuit protection, battery short-circuit protection, resettable, and is used for any hot-swappable applications and needs to limit excessive Current rushing system to prevent damage to connectors, PCB wiring and downstream devices.

eFuse compares traditional fuse and PTC resettable fuse

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

The blown fuse is one-time 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 turns from a low resistance state to a high resistance state to provide protection. When the fault is removed, the PTC resettable fuse cools down and Reset to low impedance state. Different from blown fuses and PTC resettable fuses, eFuse does not limit current based solely on heating, but measures 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 is overheated. . Compared with traditional fuses, eFuse has the following significant advantages:

・Minimum changes in parameters during over-temperature operation

・ Will not be destroyed after failure

・ Adjustable current limit

・ The enable pin turns on or off the device

・ The fault pin reports a fault that has occurred to control logic circuits or other power rails

・ Soft start to limit inrush current

・ Voltage clamp to prevent the load from being affected by voltage spikes

・ Latch or automatic reset selection, if the load is restored, everything will be reset without restarting the power supply

・ Reverse current blocking

Table 1 lists the advantages of eFuse over polymer positive temperature coefficient (PPTC) resettable fuses.

Efficient, reliable and compact eFuse optimized server and data center power supply design

Table 1: eFuse vs. PPTC resettable fuse

eFuse vs. hot-swappable controller

Although the hot-swap controller provides advanced features and diagnostics, it can increase the current limit by using different FETs, and has a strict tolerance current, but it is difficult to guarantee operation in SOA, and the price is higher. The eFuse can ensure that it always runs within the SOA, provides real-time thermal feedback, and can increase the current limit by connecting eFuses in parallel, saving board space and providing higher cost performance.

eFuse is easy to connect in parallel 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. We can increase the output current capability by connecting eFuse in parallel. 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. A high level represents normal operation. The middle level represents the thermal shutdown mode, and the low level represents the output is completely shut down.

Efficient, reliable and compact eFuse optimized server and data center power supply design

Figure: 12 V eFuse parallel demonstration

ON Semiconductor’s efficient, reliable and compact eFuse lineup

In the 3 V to 5 V power supply range, ON Semiconductor’s eFuse mainly includes NIS5135, NIS5452 and will soon launch NIS2205, NIS2x5x, NIS3x5x, NIS6452, NIS6150, NIS6350, NIS800x, and the on-resistance ranges from 33 m? 6? 8 to 200 m? 6-8, the current is from 1 A to 5 A. Among them, NIS6452, NIS6150, and NIS6350 have integrated reverse current blocking (RCP) features. NIS6150 and NIS6350 have also passed 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 reference voltage to ground, thereby realizing current monitoring.

For the 12V power supply, ON Semiconductor mainly provides NIS5020/NIS5021, NIS5820, NIS5232, NIS2x2x and will soon launch NIS5420, NIS2402 and NIS3220. The on-resistance ranges from 14 m? 6? 8 to 100 m? 6? 8, and the current ranges from 2.4 A to 12 A. Among them, NIS5020 does not have an IMON pin, but the load current can be measured by detecting the Rlim voltage, thereby achieving system-level enhancements. For related application notes, please refer to AND9685/D.

Efficient, reliable and compact eFuse optimized server and data center power supply design

Picture: NIS5020 measures load current by detecting Rlim voltage

During hot swap, the power input stage is usually susceptible to voltage spikes and transients. ON Semiconductor’s eFuse integrated overvoltage protection can provide fast response and limit the output voltage, making it less susceptible to voltage transients. Some applications require delaying the output turn-on after hot insertion to stabilize the input voltage. For related application notes, please refer to AND9672/D.

Efficient, reliable and compact eFuse optimized server and data center power supply design

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

In addition, ON Semiconductor is about to launch 24 V NIS6124 and 48 V high current eFuse. NIS6124 provides 40 V withstand voltage for 24 to 36 V. The 48 V series features: high-side eFuse over-current shutdown, 48V applications up to 80V peak input Voltage, DC capacity exceeds 120 A and current capacity can be expanded by adding MOSFET, active excitation inrush current limit of capacitive load, V2 automatic retry function. The 48 V eFuse can be tested immediately, the PCB can be simplified or modified as required, and it can be used as a reference design.

Reliability test

ON Semiconductor’s eFuses have undergone repeated short-circuit reliability tests (AEC-Q100-012). The test was carried out under the conditions of 25°C and -40°C to provide the highest thermal offset and stress. After running for 100,000 to 1 million cycles, there were no functional problems and no changes in on-resistance or other parameters. Compared with competitors, ON Semiconductor’s eFuse has better surge performance.

Summarize

The safety and reliability of power supplies for servers and data centers are of paramount importance. eFuse integrates over-current, over-heat and over-voltage protection, and provides diagnostic and control functions. It has more advantages than traditional fuses, PTC resettable fuses, and hot-swappable controllers. It is a cost-effective alternative. ON Semiconductor provides an efficient, reliable and compact eFuse solution lineup, including 3 V to 12V power supply range and the upcoming 24V and 48 V high current eFuse, built-in real-time diagnostic function, precision control and multiple protection features to ensure that it always works in SOA , Fast response, repeated short circuit reliability test, to prevent the circuit from high inrush current, voltage spikes and heat dissipation damage, performance and reliability are better than competitors, such as the use of unique 3-state enable/fault pin , EFuse can be connected in parallel to enhance current capability, new features of IMON can realize output current monitoring, hot-plug startup delay to realize system-level enhancement, etc.

The Links:   LM150X05-B2 2DI100A-120

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