Diodes Incorporated 1SMB5938B-13

Overview

1SMB5938B-13 from Diodes Incorporated is a 3.0W surface-mount power Zener diode with nominal zener voltage of 36V (±5% tolerance), maximum zener impedance of 10.4Ω at 38mA test current, and ESD rating >16kV per HBM. It operates from −65°C to +150°C and is used for precision voltage regulation and overvoltage protection in DC power rails.

For engineers reviewing the 1SMB5938B-13 datasheet, 1SMB5938B-13 pinout, 1SMB5938B-13 application, or 1SMB5938B-13 equivalent, key selection criteria include zener voltage accuracy, thermal resistance (226°C/W), power derating above +25°C, and SMB package compatibility with automated SMT assembly.

Technical Context

This Zener diode functions as a two-terminal voltage reference device, maintaining stable reverse-biased breakdown at 36V under controlled current conditions. Its design supports low dynamic impedance (10.4Ω) and tight voltage tolerance (±5%) to ensure consistent clamping performance across temperature and load variations.

Thermal management is defined by junction-to-ambient thermal resistance of 226°C/W on FR-4 PCB and junction-to-terminal resistance of 25°C/W, enabling reliable 3.0W dissipation at TL = +75°C with linear derating above that point.

Key Specifications

Pinout & Package

The 1SMB5938B-13 uses an SMB (DO-214AA) surface-mount plastic package with cathode band marking on the top surface. Polarity is unambiguous: the banded end is the cathode; the opposite end is the anode.

Key Features

Applications

Availability

1SMB5938B-13 is available at Aetrix Electronics and suitable for industrial power supply regulation, automotive body control modules, telecom DC-DC converter feedback, and medical diagnostic equipment requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for 1SMB5938B-13 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, headquartered in Plano, Texas, with design, manufacturing, and sales operations across Asia, Europe, and North America.

The SMB-series Zener diodes are engineered for high-power, high-reliability voltage regulation in space-constrained SMT applications-targeting automotive, industrial, and communications infrastructure where thermal robustness and process compatibility are critical.

FAQ

What is the maximum continuous reverse voltage the 1SMB5938B-13 can withstand without breakdown?

The 1SMB5938B-13 has a nominal zener voltage of 36V with a guaranteed range of 34.2V to 37.8V at 38mA test current. Below this threshold-specifically at VR = 27.4V-the reverse leakage current is limited to 0.25µA max. Sustained reverse voltage exceeding 37.8V will cause controlled breakdown and power dissipation governed by external current limiting.

How does the thermal derating work above +25°C ambient temperature?

Above +25°C, the 1SMB5938B-13's power dissipation must be linearly reduced at 4.4mW/°C. Starting from 550mW at +25°C, it reaches 3.0W only when mounted on a heatsink at TL = +75°C. The junction-to-ambient thermal resistance is 226°C/W on standard FR-4 PCB per Diodes Inc.'s AP02001 pad layout.

Is the 1SMB5938B-13 compatible with lead-free reflow soldering processes?

Yes-the device features matte tin plating on a copper alloy leadframe and is rated for moisture sensitivity level 1 per J-STD-020. It supports standard Pb-free reflow profiles (peak 260°C) without pre-bake, and its UL 94V-0 plastic case withstands repeated thermal cycling without delamination or cracking.

Can the 1SMB5938B-13 replace older through-hole zeners like 1N5357B in new designs?

Yes, but only with PCB layout revision: the SMB package (DO-214AA) replaces axial DO-41 or radial DO-15 footprints. Electrical characteristics-including 36V VZ, 10.4Ω Z_ZT, and 3.0W rating-are functionally aligned with 1N5357B, but thermal performance differs due to SMT vs. through-hole mounting geometry and PCB copper area utilization.