Diodes Incorporated 1SMB5955B-13

Overview

1SMB5955B-13 from Diodes Incorporated is a 3.0W surface-mount power Zener diode with nominal zener voltage of 180V (min 171V, max 189V), ±5% tolerance, and 2.1mA test current. It provides precise voltage regulation in overvoltage protection circuits for industrial power supplies and DC bus clamping applications.

For engineers reviewing the 1SMB5955B-13 datasheet, 1SMB5955B-13 pinout, 1SMB5955B-13 application, or 1SMB5955B-13 equivalent, key selection criteria include zener voltage accuracy at 2.1mA, dynamic impedance of 900Ω at IZT, maximum reverse leakage of 0.25µA at 136.8V, and thermal resistance of 226°C/W junction-to-ambient.

Technical Context

This Zener diode operates in reverse breakdown mode to maintain stable reference voltage under varying load and temperature conditions. Its 3.0W power dissipation rating applies at TL = +75°C with derating above that temperature, and it exhibits a typical temperature coefficient near +0.12 mV/°C for 180V devices per Figure 2.

The device uses an SMB package with cathode band polarity marking and achieves ESD robustness of >16kV HBM. Its low leakage (≤0.25µA at VR = 136.8V) and controlled dynamic impedance support precision regulation in high-impedance sensing and feedback paths.

Key Specifications

Pinout & Package

Package: SMB (Surface Mount Small Outline), molded plastic case rated UL 94V-0, cathode band polarity marking, 0.096 g weight.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Zener diode voltage regulation applications.

Compared with 1N5955B and SMBJ180A, the 1SMB5955B-13 uniquely balances SMT compatibility, 3.0W continuous dissipation, and ±5% DC regulation accuracy-making it optimal for space-constrained, thermally managed voltage reference and clamping roles.

Availability

1SMB5955B-13 is available at Aetrix Electronics and suitable for industrial power supplies, DC bus protection, high-voltage sensor references, and programmable threshold detectors requiring stable component supply and RoHS-compliant sourcing.

Supply support for 1SMB5955B-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.

This device belongs to the SMB-series 3.0W Zener diode family, engineered for high-reliability voltage regulation and overvoltage protection in industrial, computing, and communications power systems.

FAQ

What is the maximum continuous power dissipation for 1SMB5955B-13 at +25°C ambient?

At TA = +25°C, the maximum continuous power dissipation is 550 mW, with linear derating of 4.4 mW/°C above that temperature. This value reflects thermal limitations on standard FR-4 PCBs per Diodes Inc.'s AP02001 pad layout, not the 3.0W rating which applies only at TL = +75°C (lead temperature).

How does the 900Ω dynamic impedance affect regulation performance?

The 900Ω Z_ZT at 2.1mA means a 1mA change in zener current causes ~0.9V shift in output voltage. This defines regulation sensitivity in feedback loops and must be accounted for in divider network design to maintain target accuracy under load variation.

Is 1SMB5955B-13 suitable for use in life support equipment?

No. Diodes Incorporated explicitly prohibits use of this product in life support devices or systems without written CEO approval. Its qualification excludes safety-critical medical applications per the Life Support Notice in DS32125 Rev. 8-2.

What does the "B955" marking code indicate on the device body?

B955 is the top-side laser marking code identifying the 1SMB5955B variant. It corresponds to the 180V nominal zener voltage and is used for traceability and visual verification during incoming inspection and assembly verification.