STMicroelectronics STPS340UF

Overview

STPS340UF from STMicroelectronics is a 40 V, 3 A surface-mount Schottky rectifier in SMB Flat package, featuring low forward voltage drop (0.52 V at 3 A, 125 °C), low thermal resistance (15 °C/W junction-to-lead), and avalanche rating for robust transient handling - deployed in telecom power supplies, set-top box DC/DC converters, and battery charger freewheeling paths.

For engineers reviewing the STPS340UF datasheet, STPS340UF pinout, STPS340UF application, or STPS340UF equivalent, this device is selected for high-frequency, low-loss rectification where thermal management under 105–115 °C ambient and fast reverse recovery (<10 ns) are critical in compact SMPS designs.

Technical Context

This Schottky diode operates as a unidirectional, low-VF power rectifier with no minority-carrier storage delay, enabling operation up to several MHz in synchronous buck or flyback secondary-side circuits. Its junction temperature limit of 150 °C and avalanche-rated capability (90 W peak, 10 µs) support reliable operation under repetitive surge and inductive kick conditions.

The SMB Flat package provides optimized thermal performance (R_th(j-l) = 15 °C/W) and mechanical stability for PCB-mounted high-current paths. Device conduction loss is quantified by P = 0.42 × I_F(AV) + 0.050 × I_F(RMS)², confirming suitability for continuous 3 A average current at ≤115 °C ambient without heatsink.

Key Specifications

Pinout & Package

SMB Flat package: surface-mount, cathode-banded, 2-terminal discrete diode with leads on opposite sides; optimized for automated placement and thermal conduction via PCB copper pads.

Key Features

Applications

Equivalent & Alternatives

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

Compared with VS-3EYH04-M3/54 and SB340-E3/54, STPS340UF delivers superior thermal performance (15 °C/W vs. ≥25 °C/W) and lower high-temperature V_F, making it optimal for space-constrained, high-efficiency 3–4 A SMPS where junction temperature control is critical.

Availability

STPS340UF is available at Aetrix Electronics and suitable for telecom power supplies, set-top box power supplies, and battery chargers requiring stable component supply with consistent lead times and full traceability.

Supply support for STPS340UF 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 analog, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

STPS340UF belongs to ST's high-efficiency Schottky rectifier product line, engineered specifically for high-frequency, low-loss DC/DC conversion in space- and thermally-constrained power supplies.

FAQ

What is the maximum allowable ambient temperature for continuous 3 A operation in the STPS340UF?

The STPS340UF is rated for I_F(AV) = 3 A at T_L = 115 °C (lead temperature) in SMB Flat package. With recommended PCB copper area per Figure 22, this corresponds to ~85–90 °C ambient in still air. Derating is required above that; thermal simulation using R_th(j-a) curves (Figure 3) is advised for exact layout validation.

Does STPS340UF require a heatsink for 3 A operation?

No heatsink is required. The SMB Flat package achieves R_th(j-l) = 15 °C/W and supports 3 A continuous current at T_L = 115 °C using only standard FR4 PCB copper pours (≥3.44 × 5.84 mm per lead, 35 µm thickness). Heatsinks add unnecessary cost and volume unless ambient exceeds 90 °C.

How does the avalanche rating of STPS340UF improve reliability in real-world designs?

The 90 W peak avalanche power rating (at 10 µs, T_j = 125 °C) allows the diode to safely absorb inductive energy from transformer leakage or MOSFET turn-off spikes without catastrophic failure. This eliminates need for external clamping circuits in cost-sensitive flyback or forward converters.

Can STPS340UF replace STPS340U in existing designs?

Yes - STPS340UF (SMB Flat) and STPS340U (SMB) share identical electrical specs and pinout, but differ in package profile: SMB Flat has lower height (1.10 mm max vs. 2.45 mm) and improved thermal resistance (15 vs. 25 °C/W). Layout adaptation is needed for footprint and solder mask, but electrical behavior is interchangeable.