Diodes Incorporated 1N5256B-T

Overview

1N5256B-T from Diodes Incorporated is a 30V, ±5% tolerance, 500mW surface-mount Zener diode in a hermetic DO-35 glass package, designed for precision voltage regulation and reference applications in power supply feedback loops, overvoltage protection circuits, and analog signal conditioning stages.

For engineers reviewing the 1N5256B-T datasheet, 1N5256B-T pinout, 1N5256B-T application, or 1N5256B-T equivalent, key selection criteria include its 30V nominal Zener voltage with ±5% tolerance, 4.2mA test current, 49Ω dynamic impedance at I_ZT, +0.091%/°C temperature coefficient, and DO-35 mechanical compatibility with legacy through-hole layouts.

Technical Context

This discrete Zener diode operates in reverse breakdown to maintain stable voltage across its terminals under varying load and temperature conditions. Its 30V nominal Zener voltage is specified at 4.2mA test current, with 49Ω dynamic impedance (Z_ZT) ensuring low output variation under small-signal perturbations.

The device exhibits a positive temperature coefficient of +0.091%/°C, indicating predictable V_Z drift with rising junction temperature. Its hermetic glass DO-35 package provides moisture resistance (J-STD-020 Level 1) and thermal stability up to +175°C operating temperature.

Key Specifications

Pinout & Package

DO-35 glass axial package with cathode band marking; leads are Sn96.5Ag3.5 solderable per MIL-STD-202 Method 208. Weight: 0.13g. Dimensions: A ≤25.4mm, B ≤4.00mm, C ≤0.60mm, D ≤2.00mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MMSZ5256B and 1N4749A, the 1N5256B-T offers mid-range power (500mW), DO-35 compatibility with legacy through-hole tooling, and predictable +0.091%/°C drift-making it suitable for repair, replacement, and industrial designs requiring hermetic reliability without SMT rework.

Availability

1N5256B-T is available at Aetrix Electronics and suitable for industrial power supplies, analog sensor interfaces, overvoltage protection circuits, and legacy equipment repair requiring stable component supply and DO-35 mechanical compatibility.

Supply support for 1N5256B-T 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 and manufacturing operations across Asia and the Americas.

The 1N52xxB series belongs to Diodes' legacy Zener diode product line, engineered for general-purpose voltage regulation and reference applications where hermetic reliability, tight tolerance, and thermal stability are prioritized over ultra-low impedance or SMT miniaturization.

FAQ

Is the 1N5256B-T still in active production?

No-the 1N5256B-T is officially obsolete per Diodes Incorporated's DS18006 Rev. 19 (September 2019). It has been superseded by the MMSZ5256B for new designs. However, Aetrix Electronics maintains limited legacy stock for repair and maintenance of existing systems requiring DO-35 form factor compatibility.

What is the maximum reverse voltage before breakdown?

The 1N5256B-T begins controlled Zener breakdown at its nominal 30V rating, with guaranteed operation between 28.5V and 31.5V at 4.2mA test current. Its absolute maximum non-destructive reverse voltage is not specified, but sustained operation above 31.5V risks exceeding its 500mW power limit unless current is strictly limited by an external series resistor.

Can this diode be used in place of a 1N4749A?

Electrically, both regulate at 30V with ±5% tolerance, but the 1N5256B-T has lower power rating (500mW vs. 1W), higher Z_ZT (49Ω vs. 35Ω), and different temperature coefficient (+0.091%/°C vs. –0.0005%/°C). Substitution is acceptable only if load current remains below ~16mA and thermal design accommodates DO-35's 300°C/W R_θJA.

Does the DO-35 package support automated pick-and-place assembly?

The DO-35 package is not designed for standard SMT pick-and-place; it lacks standardized tape-and-reel carrier geometry for machine feeding and requires manual or semi-automated placement. While the -T suffix indicates tape-and-reel packaging, the component itself remains axial-leaded and must be mounted using through-hole or hand-solder processes-not reflow soldering.