Diodes Incorporated 1SMB5921B-13

Overview

1SMB5921B-13 from Diodes Incorporated is a 3.0W surface-mount power Zener diode with nominal zener voltage of 6.8V (±5%), 55.1Ω dynamic impedance at 2.5mA test current, and 220mA maximum zener current. It provides precise voltage regulation in power supply rails, overvoltage protection circuits, and reference voltage generation for industrial DC-DC converters.

For engineers reviewing the 1SMB5921B-13 datasheet, 1SMB5921B-13 pinout, 1SMB5921B-13 application, or 1SMB5921B-13 equivalent, key selection criteria include zener voltage tolerance, thermal resistance (226°C/W), ESD rating (>16kV HBM), SMB package compatibility, and derating behavior above +25°C ambient.

Technical Context

This Zener diode operates in reverse breakdown mode to maintain stable voltage across its terminals under varying load and line conditions. Its 6.8V nominal zener voltage is specified at 2.5mA test current, with dynamic impedance of 55.1Ω and knee impedance of 200Ω - indicating sharp regulation onset and low AC voltage variation during transient load shifts.

The device uses a planar silicon junction structure with cathode band polarity marking, optimized for automated SMT assembly on FR-4 PCBs. Thermal performance is defined by R_θJA = 226°C/W (free-air) and R_θJT = 25°C/W (junction-to-terminal), enabling reliable 3.0W dissipation only when mounted per AP02001 pad layout and limited to 550mW at +25°C ambient.

Key Specifications

Pinout & Package

Package: SMB (Surface Mount Bandolier), molded plastic case rated UL 94V-0, 0.096g weight, cathode band polarity marking, moisture sensitivity level 1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BZX84-C6V8 and 1N5338B, the 1SMB5921B-13 uniquely balances 3.0W SMT-compatible power handling, industry-standard ±5% tolerance, and Class 3 ESD robustness - making it optimal for mid-power industrial regulation where both automation yield and thermal reliability matter.

Availability

1SMB5921B-13 is available at Aetrix Electronics and suitable for industrial power supplies, automotive body control modules, LED driver protection, and telecom interface circuits requiring stable component supply with full traceability and lifecycle support.

Supply support for 1SMB5921B-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 centers across Asia and manufacturing facilities in China, Taiwan, and the US.

The SMB-series Zener diodes are part of Diodes' high-reliability power protection portfolio, engineered specifically for automated SMT deployment in harsh-environment industrial and automotive applications where consistent voltage regulation and ESD survivability are critical.

FAQ

What is the maximum continuous power dissipation for 1SMB5921B-13 at +75°C lead temperature?

The device is rated for 3.0W continuous power dissipation when the lead temperature (T_L) is held at +75°C, with linear derating of 40mW/°C above that point. This requires proper PCB copper area per AP02001 layout to achieve effective heat transfer from the SMB package terminals.

Does 1SMB5921B-13 meet RoHS 3 and halogen-free requirements?

Yes - it complies with EU Directive 2015/863/EU (RoHS 3), contains <900ppm bromine, <900ppm chlorine (<1500ppm total Br+Cl), and <1000ppm antimony compounds, and carries Diodes Incorporated's official "Green" designation per their quality documentation.

How is polarity identified on the 1SMB5921B-13 package?

Polarity is marked by a visible cathode band on the top surface of the SMB package, aligned with the cathode terminal. The band corresponds to the cathode pin in the standard SMB outline, and must be oriented toward the higher-potential node in reverse-bias operation.

What is the typical zener voltage temperature coefficient for this device?

Based on Figure 2 in DS32125 Rev. 8-2, the 6.8V-rated 1SMB5921B exhibits a typical temperature coefficient of approximately +3.5mV/°C - meaning its zener voltage increases by ~3.5mV per degree Celsius rise in junction temperature.