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Home > Products > Discrete Semiconductor Products > Diodes > Zener > Single Zener Diodes

Diodes Incorporated 1N5257B-T

Name: 1N5257B-T
Brand: Diodes Incorporated
SKU: 1N5257B-T
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 1N5257B-T

Manufacturer:: Diodes Incorporated

Category:: Single Zener Diodes

Package:: DO-204AH, DO-35, Axial

Datasheet:: 1N5257B-T.pdf

Description:: DIODE ZENER 33V 500MW DO35

Quantity:: RFQ Add To RFQ list

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Inventory:4,374

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Product details

Overview

1N5257B-T from Diodes Incorporated is a 33 V, ±5% tolerance, 500 mW surface-mount Zener diode in DO-35 glass package, designed for precision voltage regulation and reference applications in power supply feedback loops, overvoltage protection circuits, and analog signal conditioning. It features 58 Ω dynamic impedance at 3.8 mA test current, +0.092 %/°C temperature coefficient, and operates across –65°C to +175°C.

For engineers reviewing the 1N5257B-T datasheet, 1N5257B-T pinout, 1N5257B-T application, or 1N5257B-T equivalent, this page delivers verified electrical specs, thermal behavior, mechanical dimensions, RoHS-compliant terminal finish (Sn96.5Ag3.5), and direct replacement guidance against MMSZ5257B.

Technical Context

This Zener diode operates in reverse breakdown with tightly controlled V_Z = 31.35–34.65 V at I_ZT = 3.8 mA, delivering stable reference voltage under varying load and temperature conditions. Its low leakage (I_R ≤ 0.1 µA at V_R = 25 V) and predictable TC (+0.092 %/°C) support high-accuracy analog designs.

The DO-35 hermetic glass package ensures long-term stability and moisture resistance (J-STD-020 Level 1), while the cathode band polarity marking and Sn96.5Ag3.5 lead finish guarantee reliable solderability per MIL-STD-202 Method 208.

Key Specifications

Parameter	Value and Actual Design Meaning
Zener Voltage (V_Z)	33 V nominal, 31.35–34.65 V range at 3.8 mA - defines precise regulation point for feedback or clamp circuits
Power Dissipation (P_D)	500 mW - sets maximum continuous DC power handling at T_L ≤ 75°C with 9.5 mm lead length
Zener Impedance (Z_ZT)	58 Ω at I_ZT = 3.8 mA - determines AC ripple rejection and regulation stiffness under dynamic load
Temperature Coefficient (TC)	+0.092 %/°C - quantifies V_Z drift with ambient temperature, critical for wide-temperature-range references
Reverse Leakage (I_R)	≤ 0.1 µA at V_R = 25 V - ensures minimal error current in high-impedance bias/reference nodes
Operating Temperature	–65°C to +175°C - supports deployment in automotive engine compartments and industrial control enclosures
Package	DO-35 glass case - provides hermetic sealing, thermal stability, and compatibility with legacy through-hole reflow profiles

Pinout & Package

DO-35 glass axial package with cathode band marking; two-terminal device requiring no orientation-specific PCB footprint beyond polarity-aware placement.

Pin/Terminal	Circuit Role	Design Meaning
Anode	Forward conduction terminal / Zener cathode reference ground node	Connected to circuit ground or lower-potential rail in shunt regulator configuration
Cathode	Reverse-biased Zener terminal / regulated output node	Connected to input rail or feedback node; voltage clamped to V_Z when reverse biased above breakdown

Key Features

Feature	Design Value
±5% Zener voltage tolerance	Enables tight regulation without post-production trimming in cost-sensitive power supplies
Hermetic glass DO-35 package	Prevents moisture ingress and parameter drift over decades of operation in humid environments
Lead-free Sn96.5Ag3.5 finish	Ensures solder joint reliability and compliance with EU RoHS 2015/863/EU without Pb-based alternatives
300 °C/W junction-to-ambient thermal resistance	Defines derating curve: full 500 mW usable only below 75°C ambient with specified lead length

Applications

Switch-Mode Power Supply Feedback

Overvoltage Clamp Circuit

Use Scenario: Regulating output voltage in isolated flyback converters using optocoupler-coupled feedback.

IC Role / Device Role / Timing Role: Shunt reference providing stable 33 V threshold to TL431-like comparator input.

Use Value: Maintains ±1% output accuracy across line/load/temperature with minimal external components.

Use Scenario: Protecting microcontroller I/O pins from transient surges on 24 V industrial sensor lines.

IC Role / Device Role / Timing Role: Passive clamp limiting voltage to 33 V before reaching downstream ESD protection diodes.

Use Value: Absorbs up to 500 mW surge energy without latch-up or parametric shift, preserving system uptime.

Analog Voltage Reference

Current Source Biasing

Use Scenario: Generating stable bias for op-amp based instrumentation amplifiers in medical sensor front-ends.

IC Role / Device Role / Timing Role: Precision reference node for resistor-divider networks setting gain and offset.

Use Value: Delivers <10 ppm/°C effective drift via +0.092 %/°C TC and low thermal hysteresis in DO-35 glass.

Use Scenario: Setting constant current for LED driver biasing in automotive interior lighting modules.

IC Role / Device Role / Timing Role: Fixed-voltage reference establishing I_SET in constant-current mirror configurations.

Use Value: Enables ±2% current matching across temperature due to stable V_Z and low Z_ZT.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MMSZ5257B	Surface-mount SOD-123 package; same 33 V, ±5%, 500 mW rating; Z_ZT = 55 Ω at 3.8 mA	Replaces 1N5257B-T in space-constrained PCBs; requires re-layout for SMT vs. axial DO-35	Select for automated assembly and reduced board area; verify thermal pad layout for 500 mW dissipation
1N4755A	1 W power rating; 33 V, ±5%; DO-41 package; Z_ZT = 35 Ω at 38 mA; higher I_ZT	Supports higher-power regulation where 1N5257B-T would thermally saturate	Choose when >500 mW continuous dissipation is required; accept larger footprint and different test current

Compared with MMSZ5257B and 1N4755A, the 1N5257B-T offers legacy DO-35 compatibility and proven long-term stability in glass packaging, while trading off SMT automation benefits and higher-power capability respectively.

Availability

1N5257B-T is available at Aetrix Electronics and suitable for switch-mode power supply feedback, overvoltage clamp circuits, and analog voltage reference applications requiring stable component supply despite its obsolete status.

Supply support for 1N5257B-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 high-stability voltage reference and regulation in industrial, computing, and consumer power systems.

FAQ

Is the 1N5257B-T still in active production?

No - Diodes Incorporated has discontinued the 1N5257B-T and marked it obsolete per DS18006 Rev. 19. Aetrix Electronics maintains limited legacy stock and supports last-time buys with full traceability and documentation, including original date codes and RoHS compliance records.

What is the recommended replacement for 1N5257B-T in new designs?

The MMSZ5257B is Diodes Incorporated's designated SMT replacement, sharing identical electrical specs (33 V, ±5%, 500 mW) and RoHS compliance. It requires PCB redesign for SOD-123 footprint but enables automated assembly and improved thermal performance with proper copper pour.

Can 1N5257B-T be used in place of 1N4755A?

Only in low-power applications ≤500 mW. The 1N4755A is rated for 1 W and uses higher test current (38 mA vs. 3.8 mA), resulting in lower Z_ZT (35 Ω) and better regulation under heavy load. Substituting 1N5257B-T risks thermal runaway or voltage drift above 500 mW.

Does the DO-35 package support reflow soldering?

Yes - the DO-35 glass package is qualified for IR reflow per J-STD-020 Level 1. Peak temperature must not exceed 260°C for ≤10 seconds, and thermal shock must be minimized. Hand-soldering requires preheating and <3 sec contact time with 350°C iron to avoid glass fracture.

1N5257B-T Specifications

Product attributes: Attribute value

Manufacturer:: Diodes Incorporated

Series:: -

Package/Case:: DO-204AH, DO-35, Axial

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Voltage - Zener (Nom) (Vz):: 33 V

Tolerance:: ±5%

Power - Max:: 500 mW

Impedance (Max) (Zzt):: 58 Ohms

Current - Reverse Leakage @ Vr:: 100 nA @ 25 V

Voltage - Forward (Vf) (Max) @ If:: 1.1 V @ 200 mA

Operating Temperature:: -65°C ~ 200°C

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: DO-35

1N5257B-T FAQ

1.How can I place an order for 1N5257B-T through Aetrix?

Please submit a Request for Quotation (RFQ) for 1N5257B-T on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for 1N5257B-T reliable?

The price and inventory of 1N5257B-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1N5257B-T is usually 5 days.

3.What payment methods are accepted for 1N5257B-T?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1N5257B-T transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 1N5257B-T?

1N5257B-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 1N5257B-T order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for 1N5257B-T?

For technical support, including 1N5257B-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1N5257B-T requirements.

6.How does Aetrix verify that 1N5257B-T is sourced from the original manufacturer or authorized distributors?

All 1N5257B-T products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that 1N5257B-T meets industry standards.

7.What is the process for return or replacement of 1N5257B-T?

All 1N5257B-T units undergo pre-shipment inspection (PSI). If there is an issue with 1N5257B-T, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The 1N5257B-T part is unused and in its original packaging.

Return procedure for 1N5257B-T:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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