RS31215 - Precision eFuse with 16.5V OVP & IMON

RS31215 – 3.3V, 15A eFuse with Current Monitoring and Hot-Swap Protection

The RS31215 from Reed Semiconductor is a highly integrated 3.3V, 15A electronic fuse (eFuse) designed to provide reliable power-path protection, current monitoring, and hot-swap control for low-voltage, high-current applications. Featuring an integrated 2.7mΩ pass MOSFET, the RS31215 combines low-loss power distribution with programmable protection and monitoring functions in a compact 4mm × 4mm LGA-26 package.

Designed for 3.3V power rails, the RS31215 provides an adjustable 2A to 15A current limit, fast short-circuit protection, and configurable fault response. Its integrated current-monitor output and downstream load-start handshake functionality make it particularly suitable for server systems, PCIe add-in cards, networking equipment, and power distribution architectures supplying point-of-load (PoL) converters.

Low-Resistance 15A Power Path for 3.3V Systems

The RS31215 integrates a low-resistance 2.7mΩ pass MOSFET to support efficient power delivery while minimizing conduction losses. With an adjustable current limit ranging from 2A to 15A, the device allows designers to tailor protection thresholds to the requirements of individual power rails and downstream loads.

The integrated power path eliminates the need for a separate external pass MOSFET, reducing component count and simplifying system design. An adjustable output slew rate provides additional control over power-up behavior, helping manage output voltage transitions during startup.

These features make the RS31215 an effective solution for protecting high-current 3.3V rails in compact, power-dense electronic systems.

Fast Short-Circuit and Configurable Overcurrent Protection

The RS31215 provides fast short-circuit protection with a typical response time of less than 400ns, helping protect downstream circuitry against potentially damaging fault conditions.

An adjustable overcurrent blanking timer allows the device to accommodate temporary load-current transients without immediately triggering fault handling. This is particularly useful in systems where downstream loads experience brief current surges during normal operation.

The device also supports configurable Latch-Off or Auto-Retry fault response, including programmable retry count and delay between retries.

Two device variants provide different overcurrent protection behaviors:

• RS31215A: Current Limiter
• RS31215B: Circuit Breaker

This selection allows designers to choose the appropriate overcurrent protection approach for their system architecture and fault-management requirements.

Input Voltage and Thermal Protection

Designed specifically for 3.3V power distribution, the RS31215 integrates multiple protection mechanisms to support reliable operation under abnormal supply and load conditions.

An adjustable input undervoltage lockout (UVLO) threshold allows designers to establish the minimum acceptable input voltage before enabling the power path.

Fixed 3.7V input overvoltage protection provides an additional safeguard against excessive input voltage, while integrated overtemperature protection helps protect the device during elevated thermal conditions.

Together with the adjustable current limit and short-circuit response, these functions provide coordinated protection for sensitive downstream electronics.

Accurate Current Monitoring and Power Management

The RS31215 includes an accurate current-monitor output that allows the system to observe load-current conditions during operation.

Current-monitoring capability can support system diagnostics, power-management decisions, and fault analysis in applications where visibility into individual power rails is important.

An enable (EN) input provides external control over the power path, allowing the RS31215 to be incorporated into system-level startup and shutdown sequences.

The combination of current monitoring, programmable protection, and enable control makes the device suitable for power architectures requiring more than basic electronic fuse functionality.

Downstream Load-Start Handshake and Timeout Protection

A distinguishing feature of the RS31215 is its LDSTRT load-start timer, which supports a downstream readiness handshake following power-up.

After the power-good (PG) signal asserts, the load-start timer establishes a programmable interval during which the downstream load is expected to respond.

If the required response is not received within the programmed time, the RS31215 disables the pass FET, providing an additional layer of protection and startup supervision.

This functionality is valuable in systems where successful power delivery must be followed by confirmation that downstream circuitry has started correctly.

The adjustable load-detect and handshake timer helps designers coordinate power sequencing and monitor downstream startup behavior without relying exclusively on external supervisory circuitry.

Compact 4mm × 4mm LGA-26 Package

The RS31215 integrates its pass MOSFET, protection functions, current monitoring, and load-start control into a compact 4mm × 4mm, 26-pin LGA package.

This integrated approach reduces the number of discrete components required to implement a protected 3.3V power path, supporting compact PCB layouts and simplified power distribution designs.

The device is RoHS compliant and Green, making it suitable for electronic systems requiring compact packaging and environmental compliance.

Applications for 3.3V Power-Rail Protection

The RS31215 is designed for low-voltage, high-current systems requiring reliable power distribution, monitoring, and fault protection.

Typical applications include:

• Servers and Data Center Equipment: Protection and monitoring of 3.3V power distribution rails
• PCIe and Add-In Cards: Hot-swap protection and controlled startup of downstream circuitry
• Networking Equipment: Power-path protection for communication and networking subsystems
• Point-of-Load Power Distribution: Protection of 3.3V input rails supplying downstream PoL converters

By combining a low-resistance 15A power path, accurate current monitoring, fast short-circuit protection, and configurable fault management, the RS31215 provides a highly integrated solution for reliable 3.3V power distribution.

Explore Reed Semiconductor’s complete portfolio of eFuse and power-path protection solutions for additional devices supporting reliable power distribution and system protection.