1N5251 Zener Diode Equivalent & Substitute Parts

Part Overview

The 1N5251 is a through-hole zener diode rated at 22 V nominal voltage with 500 mW maximum power dissipation in a DO-35 axial package. Manufactured by SMC Diode Solutions, this component is classified as obsolete. Due to its obsolete status and limited availability from the original manufacturer, identifying equivalent and substitute parts is necessary to maintain design continuity and ensure supply chain reliability for applications requiring 22 V zener regulation.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	22	V
Power - Max	500	mW
Impedance (Max)	29	Ohms
Current - Reverse Leakage @ Vr	100 nA @ 17 V	nA
Voltage - Forward (Vf) (Max) @ If	1.1 V @ 200 mA	V
Mounting Type	Through Hole	—
Package / Case	DO-35, Axial	—
Operating Temperature	200	°C (Max)

Substitute Part Grouping Explanation

Substitution of the 1N5251 is determined by strict equivalence across the following critical parameters:

Zener Voltage (Vz): The substitute must maintain 22 V nominal zener voltage to preserve circuit regulation characteristics.

Power Dissipation (Pmax): The substitute must support 500 mW maximum power rating to ensure thermal compatibility within the application.

Package Type: The substitute must use DO-35 axial through-hole packaging to maintain mechanical and electrical compatibility with existing PCB layouts.

Impedance (Zzt): The substitute must maintain 29 Ohms maximum impedance to preserve dynamic impedance characteristics.

Reverse Leakage Current: The substitute must not exceed 100 nA @ 17 V to maintain leakage specifications.

Forward Voltage: The substitute must not exceed 1.1 V @ 200 mA to maintain forward conduction characteristics.

The 1N5251B TR PBFREE, manufactured by Central Semiconductor Corp, meets all these criteria and is classified as an active product with enhanced compliance certifications.

Parameter Comparison

Parameter	1N5251 (SMC)	1N5251B TR PBFREE (Central Semiconductor)	Match
Voltage - Zener (Nom)	22 V	22 V	✓
Power - Max	500 mW	500 mW	✓
Impedance (Max)	29 Ohms	29 Ohms	✓
Current - Reverse Leakage @ Vr	100 nA @ 17 V	100 nA @ 17 V	✓
Voltage - Forward (Vf) (Max) @ If	1.1 V @ 200 mA	1.1 V @ 200 mA	✓
Package / Case	DO-35, Axial	DO-35, Axial	✓
Mounting Type	Through Hole	Through Hole	✓
Operating Temperature (Max)	200°C	200°C	✓
Voltage - Zener Tolerance	Not specified	±5%	Enhanced
Product Status	Obsolete	Active	✓
RoHS Status	Not specified	ROHS3 Compliant	Enhanced

Engineering Selection Recommendations

The 1N5251B TR PBFREE from Central Semiconductor Corp is a direct functional equivalent to the obsolete 1N5251. Selection of this substitute is based on the following engineering factors:

Electrical Equivalence: All critical electrical parameters match the original specification, including zener voltage, power rating, impedance, leakage current, and forward voltage characteristics.

Product Status: The 1N5251B TR PBFREE is an active product with confirmed inventory availability, eliminating supply chain risk associated with the obsolete 1N5251.

Compliance Enhancement: The substitute provides ROHS3 compliance and lead-free construction (PBFREE designation), meeting modern environmental and regulatory requirements without compromising electrical performance.

Voltage Tolerance: The substitute specifies ±5% zener voltage tolerance, providing tighter control than the original part and improving circuit regulation precision.

Package Compatibility: Identical DO-35 axial through-hole packaging ensures direct mechanical substitution without PCB redesign.

Temperature Rating: Operating temperature range of −65°C to 200°C exceeds the original specification, providing enhanced thermal margin.

Frequently Asked Questions (FAQ)

Q: Can the 1N5251B TR PBFREE be used as a direct replacement for the 1N5251?

A: Yes. The 1N5251B TR PBFREE is electrically and mechanically equivalent across all specified parameters. Identical zener voltage, power rating, impedance, and DO-35 packaging enable direct substitution without circuit modification.

Q: What is the significance of the "PBFREE" designation in the part number?

A: PBFREE indicates lead-free construction, compliant with ROHS3 regulations. This designation confirms the absence of lead in the component solder and materials, meeting environmental compliance requirements for modern manufacturing and end-of-life disposal.

Q: Does the ±5% voltage tolerance of the 1N5251B TR PBFREE affect circuit performance?

A: The ±5% tolerance specification on the substitute provides tighter control than the original part. This enhances regulation precision and reduces voltage variation across the production range, improving overall circuit stability.

Q: Are there alternative part numbers for the 1N5251B TR PBFREE?

A: Yes. The following part numbers reference the same component: 1N5251BTR, 1N5251B-TR, 1N5251B. Additionally, cross-series equivalents TZX22C-TR and TZX22A-TR maintain identical electrical specifications and packaging.

Q: What is the operating temperature range for the substitute part?

A: The 1N5251B TR PBFREE operates from −65°C to 200°C, providing a wider temperature range than the original 1N5251. This extended range supports applications requiring operation across broader environmental conditions.

Q: Is the DO-35 package suitable for automated assembly?

A: The DO-35 axial package is a through-hole component designed for manual or wave soldering processes. Automated pick-and-place assembly requires axial component handling equipment. Verify assembly process compatibility with your manufacturing environment.

Q: What inventory status should be confirmed before design implementation?

A: The 1N5251B TR PBFREE has 10,491 pieces in stock as new original inventory. Confirm current availability with your component supplier before finalizing design specifications, as inventory levels may change.

Request Quote (Ships tomorrow)

Part Number

Quantity

Company

Contact Name

E-mail

Message