1N5257B-TP Zener Diode Equivalent & Substitute Parts

Part Overview

The 1N5257B-TP is a 33 V, 500 mW Zener diode manufactured by Micro Commercial Co in a DO-35 through-hole axial package. This component is classified as obsolete, which necessitates identification of equivalent and substitute parts for ongoing design requirements and production continuity. The 1N5257B-TP maintains ROHS3 compliance and is suitable for voltage regulation and protection applications across industrial and commercial electronics.

Key Parameters

Parameter	Value
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 Range	-55°C ~ 150°C
Mounting Type	Through Hole
Package / Case	DO-204AH, DO-35, Axial
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitute parts for the 1N5257B-TP are grouped based on the following critical parameters that determine functional equivalence:

Primary Substitution Criteria:

Voltage - Zener (Nom): 33 V (exact match required)
Tolerance: ±5% (exact match required)
Mounting Type: Through Hole (required for mechanical compatibility)
Package Category: Axial configuration (required for board layout compatibility)

Secondary Consideration Parameters:

Power - Max: 500 mW (minimum requirement; higher power ratings are acceptable for direct substitution)
Operating Temperature Range: Minimum -55°C to 150°C coverage (extended ranges are acceptable)
RoHS Compliance: ROHS3 status preferred for regulatory alignment

Substitutes are classified into two categories: Upgrade (direct replacement with enhanced specifications) and Similar (functionally equivalent with variations in power rating, package size, or impedance characteristics).

Parameter Comparison

Parameter	1N5257B-TP (Main)	1N5257B TR PBFREE (Upgrade)	1N4752ATR (Similar)	1N5078 (Similar)	1N5364B (Similar)	1N5748B (Similar)
Manufacturer	Micro Commercial Co	Central Semiconductor Corp	onsemi	Microchip Technology	Microsemi Corporation	Microchip Technology
Voltage - Zener (Nom) (Vz)	33 V	33 V	33 V	33 V	33 V	33 V
Tolerance	±5%	±5%	±5%	±5%	±5%	±5%
Power - Max	500 mW	500 mW	1 W	3 W	5 W	500 mW
Impedance (Max) (Zzt)	58 Ohms	58 Ohms	45 Ohms	21 Ohms	10 Ohms	90 Ohms
Current - Reverse Leakage @ Vr	100 nA @ 25 V	100 nA @ 25 V	5 µA @ 25.1 V	1 µA @ 25.1 V	500 nA @ 23.8 V	100 nA @ 23 V
Voltage - Forward (Vf) (Max) @ If	1.1 V @ 200 mA	1.1 V @ 200 mA	Not Specified	Not Specified	1.2 V @ 1 A	900 mV @ 10 mA
Operating Temperature Range	-55°C ~ 150°C	-65°C ~ 200°C	-65°C ~ 200°C	-65°C ~ 175°C	-65°C ~ 150°C	-65°C ~ 175°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	DO-35	DO-35	DO-41	Axial	T-18	DO-35
Product Status	Obsolete	Active	Active	Active	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	Not Specified	RoHS non-compliant	RoHS non-compliant

Engineering Selection Recommendations

1N5257B TR PBFREE (Upgrade Substitute)

The 1N5257B TR PBFREE manufactured by Central Semiconductor Corp is the primary recommended substitute. This part maintains identical electrical specifications (33 V, 500 mW, ±5%, 58 Ohms impedance) and package configuration (DO-35) as the 1N5257B-TP. The upgrade provides extended operating temperature range (-65°C to 200°C versus -55°C to 150°C), active product status with 5251 units in stock, ROHS3 compliance, and lead-free (PBFREE) designation. This substitute provides direct functional equivalence with improved availability and regulatory alignment.

1N5748B (Similar Substitute - DO-35 Package)

The 1N5748B manufactured by Microchip Technology is a functionally equivalent substitute in the same DO-35 package. Electrical specifications match the primary requirements: 33 V nominal voltage, 500 mW power rating, and ±5% tolerance. Operating temperature range extends to -65°C to 175°C. Impedance is specified at 90 Ohms (versus 58 Ohms for the main part), which represents a 55% increase. This part is suitable for applications where impedance variation is acceptable. Product status is active with 735 units in stock.

1N4752ATR (Similar Substitute - Higher Power, DO-41 Package)

The 1N4752ATR manufactured by onsemi provides a higher power rating (1 W versus 500 mW) in a DO-41 package. Zener voltage (33 V) and tolerance (±5%) remain identical. Impedance is 45 Ohms, providing lower impedance than the main part. Operating temperature range is -65°C to 200°C. This substitute is applicable for designs requiring increased power dissipation capability, though board layout modifications are necessary due to the larger DO-41 package footprint. Product status is active with 9869 units in stock.

1N5078 (Similar Substitute - Higher Power, Axial Package)

The 1N5078 manufactured by Microchip Technology provides the highest power rating (3 W) among substitutes in a generic axial package. Zener voltage (33 V) and tolerance (±5%) are maintained. Impedance is 21 Ohms, providing significantly lower impedance. Operating temperature range is -65°C to 175°C. This substitute is suitable for high-power regulation applications. Product status is active with 767 units in stock.

1N5364B (Similar Substitute - Highest Power, T-18 Package)

The 1N5364B manufactured by Microsemi Corporation provides the highest power rating (5 W) in a T-18 package. Zener voltage (33 V) and tolerance (±5%) are maintained. Impedance is 10 Ohms, providing the lowest impedance among all substitutes. Operating temperature range is -65°C to 150°C. This substitute is applicable for maximum power dissipation requirements. Product status is active with 43755 units in stock. Note: RoHS non-compliant status requires regulatory evaluation for new designs.

Frequently Asked Questions (FAQ)

Q: Can the 1N5257B TR PBFREE directly replace the 1N5257B-TP without circuit modifications?

A: Yes. The 1N5257B TR PBFREE maintains identical electrical specifications (33 V, 500 mW, ±5%, 58 Ohms) and package configuration (DO-35). No circuit modifications are required. The extended operating temperature range (-65°C to 200°C) and active product status make this the preferred direct replacement.

Q: What is the primary difference between the upgrade substitute and similar substitutes?

A: The 1N5257B TR PBFREE (upgrade) provides identical electrical and package specifications with improved availability and extended temperature range. Similar substitutes (1N4752ATR, 1N5078, 1N5364B, 1N5748B) maintain the 33 V zener voltage and ±5% tolerance but vary in power rating, package size, and impedance characteristics. Similar substitutes require circuit evaluation to confirm suitability.

Q: Can I use a higher power-rated substitute (1 W, 3 W, or 5 W) in place of the 500 mW 1N5257B-TP?

A: Yes, higher power-rated substitutes are functionally compatible for direct replacement in the circuit. The zener voltage (33 V) and tolerance (±5%) remain identical. Higher power ratings provide additional thermal margin and are suitable for applications where the original 500 mW rating is adequate. However, package size differences (DO-41 for 1N4752ATR, axial for 1N5078, T-18 for 1N5364B) may require board layout modifications.

Q: What is the significance of impedance differences among the substitutes?

A: Impedance (Zzt) affects voltage regulation performance under varying load conditions. Lower impedance provides better voltage regulation stability. The 1N5257B-TP specifies 58 Ohms. Substitutes range from 10 Ohms (1N5364B) to 90 Ohms (1N5748B). For precision voltage regulation applications, lower impedance substitutes (1N5078 at 21 Ohms, 1N5364B at 10 Ohms) provide superior performance. For general-purpose applications, impedance variation is typically acceptable.

Q: Are all substitutes RoHS compliant?

A: The 1N5257B TR PBFREE and 1N4752ATR are ROHS3 compliant. The 1N5078 RoHS status is not specified. The 1N5364B and 1N5748B are RoHS non-compliant. For new designs subject to RoHS regulations, use the 1N5257B TR PBFREE or 1N4752ATR.

Q: What package considerations apply when selecting a substitute?

A: The 1N5257B-TP uses a DO-35 package. Direct package-compatible substitutes are 1N5257B TR PBFREE and 1N5748B (both DO-35). The 1N4752ATR uses DO-41 (larger footprint), 1N5078 uses generic axial, and 1N5364B uses T-18 (larger footprint). Package changes require verification of board layout compatibility, lead spacing, and mounting hole positioning.

Q: Which substitute offers the best combination of availability and specifications?

A: The 1N5257B TR PBFREE provides the optimal balance: identical electrical specifications, DO-35 package compatibility, active product status with 5251 units in stock, ROHS3 compliance, and extended operating temperature range. This substitute is the recommended first choice for replacement applications.

Q: Can I use the 1N5748B as a direct substitute despite the higher impedance specification?

A: Yes. The 1N5748B maintains identical zener voltage (33 V), power rating (500 mW), tolerance (±5%), and package (DO-35). The impedance specification of 90 Ohms (versus 58 Ohms for the main part) represents a 55% increase. For applications where voltage regulation precision is not critical, this impedance variation is acceptable. For precision regulation circuits, the 1N5257B TR PBFREE is preferred due to matching impedance specifications.

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