STMicroelectronics STEF05LJR

Overview

STEF05LJR from STMicroelectronics is a latch-type electronic fuse (eFuse) designed for 5 V rail protection in high-reliability storage systems. It integrates an N-channel power MOSFET with 25 mΩ typical on-resistance (Flip Chip package), 2.5 A continuous current rating, 6.1 V output clamping voltage, and thermal latch at 160 °C. It operates from −40 °C to +125 °C junction temperature and is used in SSDs and HDD arrays for overcurrent, overvoltage, and thermal fault protection.

For engineers reviewing the STEF05LJR datasheet, STEF05LJR pinout, STEF05LJR application, or STEF05LJR equivalent, this device requires attention to its dual-function Enable/Fault pin behavior, external R_LIMIT-set current thresholds (e.g., 1.1–1.9 A short-circuit limit), dv/dt ramp control limitations (not available in Flip Chip), and package-specific thermal resistance (90 °C/W).

Technical Context

The STEF05LJR implements a precision current-sense architecture using an internal N-channel sense FET with fixed ratio to monitor load current and enforce two-tiered limiting: overload trip-point (2.5 A) and lower short-circuit clamp (1.1–1.9 A). Its voltage clamp circuit actively limits V_OUT to ≤6.8 V during input overvoltage events.

Thermal protection uses a latching shutdown at 160 °C with no auto-retry - reset requires either supply cycling or pulling the Enable/Fault pin below 0.5 V. The Enable/Fault pin serves as tri-state interface: floating/high enables operation; grounded disables output; intermediate voltage (0.8–2.0 V) signals thermal fault to monitoring circuits.

Key Specifications

Pinout & Package

STEF05LJR is packaged in Flip Chip 9-bump format (1.19 mm × 1.19 mm, 0.55 mm height), optimized for ultra-compact SSD modules and high-density PCB layouts. Exposed die attach area provides low-inductance ground path and enhanced thermal conduction.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar eFuse applications.

Compared with STEF05LJR, TCKE805M1207A offers higher current but sacrifices deterministic fault containment, while TPS25942L adds intelligence at the cost of design simplicity and component count - STEF05LJR remains optimal for compact, autonomous 5 V rail protection in storage subsystems.

Availability

STEF05LJR is available at Aetrix Electronics and suitable for solid state drives, hard disk drive arrays, and optical disc drive power management requiring stable component supply across extended product lifecycles.

Supply support for STEF05LJR includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in power management, automotive ICs, and industrial microcontrollers.

The STEF05LJR belongs to ST's eFuse portfolio targeting high-density storage and computing platforms, engineered specifically for reliable 5 V rail protection with minimal footprint and zero calibration overhead.

FAQ

What is the function of the En/Fault pin on STEF05LJR?

The En/Fault pin is a tri-state, bi-directional interface. When floating, it enables normal operation via internal pull-up. Pulling it below 0.5 V disables the output. During thermal fault, it settles at 0.8–2.0 V to signal the event to a monitoring circuit. It cannot be biased above 3.6 V and lacks dv/dt control capability in the Flip Chip variant.

How is current limiting set on STEF05LJR?

Current limiting is configured externally using a resistor (R_LIMIT) between the I-Lim+ pin and the Source pins (C1–C3). For STEF05LJR, R_LIMIT values from 15 Ω to 120 Ω set short-circuit limits between 1.1 A and 1.9 A, and overload trip-points near 2.5 A. The device uses Kelvin sensing to reject PCB trace resistance errors.

Does STEF05LJR support soft-start with external capacitor?

No. The dv/dt pin is present but not functional in the Flip Chip 9-bump package. Soft-start is fixed at ~1.4 ms (10%–90% V_OUT) and cannot be extended. This differs from the DFN10 version, which supports 0–1 nF external capacitors on the dv/dt pin to adjust ramp time up to 16 ms.

What happens after thermal shutdown occurs?

STEF05LJR enters latched shutdown: output disconnects permanently until reset. Reset requires either cycling V_CC or pulling the En/Fault pin below 0.5 V and releasing it. Unlike auto-retry versions, it does not attempt automatic recovery - ensuring fault persistence is visible to system firmware for diagnostics and safe restart protocols.