STMicroelectronics STEF05LAJR

Overview

STEF05LAJR from STMicroelectronics is a latching electronic fuse (eFuse) optimized for 5 V rail protection in high-reliability storage systems. It integrates an N-channel power MOSFET with 25 mΩ typical R_DS(on) (Flip Chip package), 2.5 A continuous current rating, 6.1 V output clamping voltage, and thermal latch at 160 °C. It operates across –40 °C to 125 °C junction temperature and supports controlled soft-start via internal dv/dt circuitry - used in SSDs and HDD arrays for overcurrent, overvoltage, and thermal fault protection.

For engineers reviewing the STEF05LAJR datasheet, STEF05LAJR pinout, STEF05LAJR application, or STEF05LAJR equivalent, this device requires attention to its dual-function Enable/Fault pin behavior, external current-limit resistor (RLimit) selection, Flip Chip 9-bump package layout constraints, and distinction between latching vs. auto-retry versions when designing fault-tolerant 5 V power distribution.

Technical Context

The STEF05LAJR 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 (ILim = 2.5 A) and short-circuit clamp (IShort ≈ 1.5 A typ. with 24 Ω RLimit). Its voltage clamp circuit actively limits VOUT to ≤6.8 V under overvoltage conditions (e.g., input surge to 8 V).

Thermal protection uses a non-degrading latch mechanism triggered at 160 °C, signaled via intermediate voltage (0.8–2.0 V) on the bi-directional Enable/Fault pin. The device features programmable turn-on slew rate (1.4 ms baseline, extendable to 16 ms with external C_dv/dt) and undervoltage lockout (3.1–4.0 V turn-on threshold with 0.1 V hysteresis).

Key Specifications

Pinout & Package

STEF05LAJR is supplied in Flip Chip 9-bump package (1.19 mm × 1.19 mm, 0.55 mm height), optimized for ultra-compact SSD and HDD controller board layouts. Exposed die attach area provides low thermal resistance (R_thJC not specified; R_thJA = 90 °C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS259211DRCT and AP22653WMX-7, STEF05LAJR uniquely combines Flip Chip miniaturization, integrated 6.1 V clamping, thermal latch with status signaling, and Kelvin-sensing compatibility - making it the only option qualified for high-density, thermally constrained storage power domains.

Availability

STEF05LAJR is available at Aetrix Electronics and suitable for solid state drives, hard disk drive arrays, and optical disc drive power distribution requiring stable component supply, long-term lifecycle support, and consistent Flip Chip 9-bump packaging.

Supply support for STEF05LAJR 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, microcontrollers, and automotive-grade analog ICs.

STEF05LAJR belongs to ST's eFuse portfolio designed specifically for high-reliability 5 V power rail protection in data storage systems - emphasizing thermal robustness, compact packaging, and seamless integration with HDD/SSD controller architectures.

FAQ

What is the function of the En/Fault pin on STEF05LAJR?

The En/Fault pin serves dual roles: when left floating or pulled high, it enables the eFuse output; when pulled low (<0.5 V), it disables the output. During thermal shutdown, it transitions to an intermediate voltage (0.8–2.0 V) to signal fault condition to host monitoring circuitry - enabling coordinated shutdown across multiple devices when daisy-chained.

How is current limiting set on STEF05LAJR?

Current limiting is configured externally using a resistor (RLimit) between the I-Lim+ pin and the Source (VOUT) terminal. For STEF05LAJR, RLimit ranges from 15 Ω to 120 Ω, setting short-circuit current (IShort) between ~1.1 A and 1.9 A, and overload trip-point (ILim) at 2.5 A - values confirmed in Table 6 of DS11527 Rev 2.

Does STEF05LAJR support soft-start adjustment?

No - the STEF05LAJR (Flip Chip version) does not support external dv/dt capacitor adjustment. Unlike the DFN10 variant, its dv/dt circuit is internal-only with fixed 1.4 ms VOUT ramp time (10–90 %). The "dv/dt" pin is not present in the Flip Chip 9-bump configuration per Figure 2 and Table 1 of DS11527 Rev 2.

What is the difference between STEF05LJR and STEF05LAJR?

STEF05LJR is the latching version; STEF05LAJR is the auto-retry version. Both share identical electrical specs and package, but STEF05LAJR automatically attempts re-enabling after thermal fault when die temperature falls below hysteresis (≈135 °C), whereas STEF05LJR remains latched until supply cycling or active EN pin reset - critical for fail-safe vs. self-recovering system requirements.