1N5259B-T Zener Diode Equivalent & Substitute Parts

Part Overview

The 1N5259B-T is a 39 V, 500 mW Zener diode manufactured by Diodes Incorporated in a DO-35 through-hole package. This component is classified as obsolete, necessitating identification of active equivalent and substitute parts for ongoing design requirements and production continuity. The 1N5259B-T serves voltage regulation and protection functions in electronic circuits requiring a nominal Zener voltage of 39 V with ±5% tolerance.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	39	V
Tolerance	±5%	—
Power - Max	500	mW
Impedance (Max)	80	Ohms
Current - Reverse Leakage @ Vr	100	µA @ 30 V
Voltage - Forward (Vf) (Max) @ If	1.1	V @ 200 mA
Operating Temperature Range	-65 to 200	°C
Mounting Type	Through Hole	—
Package / Case	DO-204AH, DO-35, Axial	—

Substitute Part Grouping Explanation

Substitution of the 1N5259B-T is determined by the following critical parameters:

Primary Substitution Criteria:

Voltage - Zener (Nom): 39 V (exact match required)
Power - Max: 500 mW (exact match required)
Mounting Type: Through Hole (exact match required)
Package / Case: DO-35 or DO-204AH (exact match required)

Secondary Substitution Criteria:

Impedance (Max): 80 Ohms (exact match required)
Operating Temperature Range: Minimum -65°C to maximum 200°C or higher (equal or superior range acceptable)
Tolerance: ±5% or ±10% (both acceptable for voltage regulation applications)

All substitute parts listed maintain identical core electrical specifications for Zener voltage, power dissipation, and impedance. Variations in tolerance, forward voltage characteristics, and reverse leakage current are within acceptable engineering parameters for this component category. Product status and compliance certifications are provided to support design and procurement decisions.

Parameter Comparison

Parameter	1N5259B-T (Diodes Inc.)	1N5259A (Microsemi)	1N5259B-1 (Microchip)	1N5259A (Microchip)	1N5259B (Microchip)	1N5259B TR PBFREE (Central Semi)
Voltage - Zener (Nom)	39 V	39 V	39 V	39 V	39 V	39 V
Tolerance	±5%	±10%	±5%	±10%	±5%	±5%
Power - Max	500 mW	500 mW	500 mW	500 mW	500 mW	500 mW
Impedance (Max)	80 Ohms	80 Ohms	80 Ohms	80 Ohms	80 Ohms	80 Ohms
Current - Reverse Leakage @ Vr	100 µA @ 30 V	100 nA @ 30 V	100 nA @ 30 V	100 nA @ 29 V	100 nA @ 30 V	100 nA @ 30 V
Voltage - Forward (Vf) (Max) @ If	1.1 V @ 200 mA	1.5 V @ 200 mA	1.5 V @ 200 mA	1.5 V @ 200 mA	1.5 V @ 200 mA	1.1 V @ 200 mA
Operating Temperature Range	-65 to 200°C	-65 to 175°C	-65 to 175°C	-65 to 175°C	-65 to 175°C	-65 to 200°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	DO-204AH, DO-35, Axial	DO-204AH, DO-35, Axial	DO-204AH, DO-35, Axial	DO-204AH, DO-35, Axial	DO-204AH, DO-35, Axial	DO-204AH, DO-35, Axial
Product Status	Obsolete	Active	Active	Active	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	Not specified	RoHS non-compliant	RoHS non-compliant	ROHS3 Compliant

Engineering Selection Recommendations

Primary Recommendation: 1N5259B TR PBFREE (Central Semiconductor Corp)

The 1N5259B TR PBFREE is the optimal substitute for the obsolete 1N5259B-T. This part maintains identical electrical specifications including 39 V nominal Zener voltage, ±5% tolerance, 500 mW power rating, and 80 Ohm impedance. The operating temperature range extends to 200°C, matching the original part. ROHS3 compliance and unlimited moisture sensitivity level (MSL 1) align with the original specification. This part is currently active with 10,614 units in stock.

Secondary Recommendation: 1N5259B (Microchip Technology)

The 1N5259B from Microchip Technology provides identical electrical performance with 39 V nominal voltage, ±5% tolerance, and 500 mW power rating. Operating temperature range is -65 to 175°C, which is 25°C lower than the original part. This part is active with 8,100 units in stock. RoHS compliance status differs from the original specification.

Alternative Recommendation: 1N5259B-1 (Microchip Technology)

The 1N5259B-1 offers equivalent electrical specifications with 39 V nominal voltage, ±5% tolerance, and 500 mW power rating. Operating temperature range is -65 to 175°C. This part is active with 922 units in stock. Selection of this part is appropriate when the reduced upper temperature limit is acceptable for the application.

Tolerance Consideration: 1N5259A Variants

Both the 1N5259A from Microsemi Corporation and the 1N5259A from Microchip Technology provide 39 V nominal voltage with ±10% tolerance. These parts are suitable for applications where ±10% voltage tolerance is acceptable. The Microsemi variant is ROHS3 compliant and active with 931 units in stock. The Microchip variant is active with 1,073 units in stock but is RoHS non-compliant.

Frequently Asked Questions (FAQ)

Q: Can the 1N5259A (±10% tolerance) be used as a direct substitute for the 1N5259B-T (±5% tolerance)?

A: The 1N5259A is electrically compatible and maintains the same 39 V nominal Zener voltage and 500 mW power rating. However, the ±10% tolerance specification is broader than the original ±5% tolerance. Selection depends on circuit requirements for voltage regulation precision. Applications requiring tighter voltage tolerance should use ±5% variants.

Q: What is the impact of the reduced operating temperature range (-65 to 175°C) in Microchip variants compared to the original (-65 to 200°C)?

A: The original 1N5259B-T and the 1N5259B TR PBFREE both support operation to 200°C. Microchip variants (1N5259B, 1N5259B-1, and 1N5259A) are rated to 175°C maximum. For applications requiring operation above 175°C, the 1N5259B TR PBFREE is the appropriate selection.

Q: Are all substitute parts available in the same DO-35 package?

A: Yes. All substitute parts listed are available in DO-35 package configuration (DO-204AH, DO-35, Axial). Direct mechanical and electrical compatibility is maintained for through-hole PCB mounting.

Q: What is the difference between reverse leakage current specifications across substitute parts?

A: The original 1N5259B-T specifies 100 µA reverse leakage at 30 V. All substitute parts specify 100 nA reverse leakage at 30 V (or 29 V for one variant), representing significantly lower leakage current. This improved characteristic does not affect substitution compatibility and provides superior performance in voltage regulation applications.

Q: How do forward voltage characteristics differ among substitute parts?

A: The original 1N5259B-T and 1N5259B TR PBFREE specify 1.1 V maximum forward voltage at 200 mA. Microchip and Microsemi variants specify 1.5 V maximum forward voltage at 200 mA. Both specifications are within acceptable parameters for Zener diode applications. Forward voltage differences are relevant only in forward-biased circuit configurations.

Q: Which substitute part has the highest inventory availability?

A: The 1N5259B TR PBFREE from Central Semiconductor Corp has the highest inventory with 10,614 units in stock, followed by the 1N5259B from Microchip Technology with 8,100 units.

Q: Are there RoHS compliance differences between substitute options?

A: The 1N5259B-T is ROHS3 compliant. Among substitutes, the 1N5259A from Microsemi and the 1N5259B TR PBFREE from Central Semiconductor are ROHS3 compliant. Microchip variants (1N5259B, 1N5259B-1, and 1N5259A) are listed as RoHS non-compliant. Design requirements for RoHS compliance should guide part selection.

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