STMicroelectronics STPS3L40UF

Overview

STPS3L40UF from STMicroelectronics is a 40 V, 3 A low-forward-voltage Schottky rectifier optimized for high-frequency switch-mode power supplies and DC/DC converters. It features a typical forward voltage drop of 0.40 V at 3 A and 125 °C, negligible switching losses, avalanche rating, and thermal resistance as low as 15 °C/W (junction-to-lead, SMB Flat Notch), enabling compact, efficient power conversion in telecom and consumer power supplies.

For engineers reviewing the STPS3L40UF datasheet, STPS3L40UF pinout, STPS3L40UF application, or STPS3L40UF equivalent, key selection criteria include its 40 V reverse voltage rating, 3 A average forward current capability, low VF performance across temperature, surface-mount SMB Flat Notch package, and suitability for high-efficiency 12–24 V output DC/DC chargers and auxiliary rails.

Technical Context

This Schottky rectifier operates with zero minority-carrier storage, eliminating reverse recovery time and associated switching losses. Its metal-semiconductor junction delivers fast unidirectional conduction with minimal forward voltage-0.40 V typ. at 3 A and 125 °C-reducing conduction loss in high-duty-cycle applications.

Thermally, it supports continuous operation up to 150 °C junction temperature and offers avalanche-rated ruggedness (95 W peak, 10 µs pulse) for transient overvoltage resilience. Package variants (SMB Flat Notch, SMB Flat, SMC) provide scalable thermal performance: R_th(j-l) = 15 °C/W (SMB Flat Notch) vs. 18 °C/W (SMC), directly impacting board-level thermal design margin.

Key Specifications

Pinout & Package

STPS3L40UF is packaged in SMB Flat Notch (order code STPS3L40UFN), a surface-mount, lead-free, UL94 V0 epoxy package with standardized footprint (5.84 × 3.44 mm). The device has two terminals: anode and cathode, with polarity marked by a notch on the cathode end.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SB340 and SS34H, STPS3L40UF delivers the lowest verified V_F at elevated temperature (0.40 V), highest avalanche energy (95 W), and best thermal resistance (15 °C/W), making it optimal for thermally constrained, high-reliability 12–24 V DC/DC outputs.

Availability

STPS3L40UF is available at Aetrix Electronics and suitable for telecom power supply, set-top box power supply, and battery charger designs requiring stable component supply, long-term lifecycle support, and RoHS-compliant sourcing.

Supply support for STPS3L40UF 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, designing and manufacturing microcontrollers, power devices, sensors, and analog ICs for automotive, industrial, and consumer markets.

STPS3L40UF belongs to ST's high-efficiency Schottky rectifier product line, engineered specifically for high-frequency, low-loss secondary-side rectification in space-constrained AC/DC and DC/DC power supplies.

FAQ

What is the maximum allowable PCB copper area for optimal thermal performance in SMB Flat Notch?

For STPS3L40UF in SMB Flat Notch, thermal resistance junction-to-ambient drops to ≤40 °C/W with ≥4 cm² total copper area (2 cm² per lead) on 35 µm FR4. Figure 10 in DS1947 shows R_th(j-a) = 4.5 °C/W at 4 cm²-enabling 2.5 W continuous dissipation with ≤37.5 °C rise above ambient.

Does STPS3L40UF require a heatsink in a 3 A, 12 V output application?

No heatsink is required. With R_th(j-l) = 15 °C/W and typical power dissipation of 1.2 W (0.40 V × 3 A), the junction-to-PCB temperature rise is only 18 °C. Standard 2 oz copper with 2 cm² per pad achieves sufficient heat spreading-verified in ST's AN5088 thermal guidelines.

How does the avalanche rating impact reliability in flyback converter designs?

The 95 W peak avalanche power (10 µs) allows STPS3L40UF to absorb energy from transformer leakage inductance spikes without failure. In flyback designs with >10% leakage, this rating prevents catastrophic failure during output short-circuit or startup transients-validated per IEC 61000-4-5 surge testing protocols.

Can STPS3L40UF replace STPS3L40S in the same footprint?

No-STPS3L40UF (SMB Flat Notch) and STPS3L40S (SMC) have incompatible footprints and thermal profiles. SMB Flat Notch measures 5.84 × 3.44 mm; SMC is 8.19 × 5.11 mm. Substitution requires PCB redesign and thermal revalidation due to R_th(j-l) difference (15 vs. 18 °C/W) and current derating curves.