Diodes Incorporated 1SMB5931B-13

Overview

1SMB5931B-13 from Diodes Incorporated is a 3.0W surface-mount power Zener diode with a nominal zener voltage of 18.0 V (±5%), 12 mA test current, 20.8 Ω dynamic impedance at I_ZT, and 0.25 µA maximum reverse leakage at 13.7 V. It operates across –65°C to +150°C and is used for precision voltage regulation in DC power supplies and overvoltage protection circuits.

For engineers reviewing the 1SMB5931B-13 datasheet, 1SMB5931B-13 pinout, 1SMB5931B-13 application, or 1SMB5931B-13 equivalent, key selection criteria include zener voltage tolerance, thermal resistance (226 °C/W), power derating above +25°C, and SMB package compatibility with automated SMT assembly.

Technical Context

This device functions as a two-terminal voltage reference diode operating in reverse breakdown mode. Its zener voltage is stabilized by avalanche and Zener mechanisms depending on voltage range - at 18 V, dominant avalanche behavior yields low temperature coefficient (~+4.5 mV/°C per Figure 2) and predictable dynamic impedance.

The SMB package enables high-power dissipation (3.0 W at T_L = +75°C) with low thermal resistance (25 °C/W junction-to-terminal). Electrical performance is specified under pulsed test conditions to minimize self-heating, and reverse leakage is guaranteed ≤0.25 µA at 76% of V_Z.

Key Specifications

Pinout & Package

Package: SMB (Surface Mount Body), molded plastic case with cathode band marking; dimensions: 3.30–3.94 mm (L) × 4.06–4.57 mm (W) × 1.96–2.21 mm (H); weight ≈ 0.096 g.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N5350B and BZX85C18, the 1SMB5931B-13 delivers superior thermal performance in SMT form factor, enabling higher reliability in thermally constrained PCBs while maintaining tight voltage tolerance and low dynamic impedance essential for precision regulation.

Availability

1SMB5931B-13 is available at Aetrix Electronics and suitable for DC power supply regulation, overvoltage clamp protection, and precision reference voltage source applications requiring stable component supply and full RoHS compliance.

Supply support for 1SMB5931B-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 part of Diodes' high-reliability power management portfolio, engineered for stable voltage reference and transient suppression in industrial, computing, and automotive power systems.

FAQ

What is the maximum continuous reverse current the 1SMB5931B-13 can handle without degradation?

The device is rated for a maximum zener test current (I_ZT) of 12 mA at 18 V, and its absolute maximum zener current (I_ZM) is 83 mA, derived from P_D/V_Z = 3.0 W / 18 V. Continuous operation beyond I_ZM risks thermal runaway and permanent parametric shift, especially above +25°C ambient.

How does the 1SMB5931B-13 perform under pulsed conditions compared to DC operation?

Per Figure 10, it supports up to 1.2 kW peak pulse power for 1 ms duration and maintains stable breakdown characteristics under 8/20 µs surges. Unlike DC operation, pulsed testing minimizes self-heating, allowing higher instantaneous currents (e.g., 83 A at 1 ms) while preserving long-term reliability and voltage stability.

Is the cathode band orientation consistent across all SMB-packaged Zeners from Diodes Incorporated?

Yes - the cathode band is always located on the same end of the SMB body, aligned with the marking code (B931 for this device). The top-view marking diagram in the datasheet confirms band position relative to the "B9xx" laser etch, ensuring unambiguous polarity identification during automated optical inspection and placement.

Can the 1SMB5931B-13 be used in parallel for higher current capability?

No - due to inherent V_Z tolerances (±5%) and mismatched temperature coefficients, paralleling multiple units causes current hogging and thermal instability. For higher current, use a single higher-power Zener (e.g., 5 W SMB variant) or implement active regulation with a pass transistor instead.