1N972B_T50R Zener Diode Equivalent & Substitute Parts

Part Overview

The 1N972B_T50R is a 30 V, 500 mW Zener diode manufactured by onsemi in a DO-35 axial through-hole package. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The 1N972B_T50R serves voltage regulation and protection applications requiring a nominal Zener voltage of 30 V with ±5% tolerance and 500 mW power dissipation capability.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	30	V
Tolerance	±5%	%
Power - Max	500	mW
Impedance (Max)	49	Ohms
Current - Reverse Leakage @ Vr	5	µA @ 22.8 V
Operating Temperature Range	-65 to 200	°C
Mounting Type	Through Hole
Package / Case	DO-35 (DO-204AH)

Substitute Part Grouping Explanation

Substitution of the 1N972B_T50R is determined by the following critical parameters:

Primary Substitution Criteria:

Voltage - Zener (Nom): 30 V
Power - Max: 500 mW
Impedance (Max): 49 Ohms
Mounting Type: Through Hole
Package compatibility: DO-35 or equivalent axial package

Secondary Considerations:

Tolerance: ±5% preferred for direct equivalence
Operating Temperature Range: Minimum -65°C to 175°C required
Current - Reverse Leakage: Specification dependent on application

Substitute parts are grouped into two categories: Direct Equivalents (matching all primary parameters including package) and Parametric Equivalents (matching electrical specifications with alternative package form factors).

Parameter Comparison

Parameter	1N972B_T50R (Main)	1N972A	1N972B-1	1N972BE3	1N5256B TR PBFREE
Manufacturer	onsemi	Microchip Technology	Microchip Technology	Microchip Technology	Central Semiconductor Corp
Voltage - Zener (Nom)	30 V	30 V	27 V	30 V	30 V
Tolerance	±5%	±10%	±5%	±5%	±5%
Power - Max	500 mW	500 mW	500 mW	500 mW	500 mW
Impedance (Max)	49 Ohms	49 Ohms	49 Ohms	49 Ohms	49 Ohms
Current - Reverse Leakage @ Vr	5 µA @ 22.8 V	5 µA @ 22.8 V	500 nA @ 21 V	5 µA @ 22.8 V	100 nA @ 23 V
Operating Temperature Range	-65 to 200°C	-65 to 175°C	-65 to 175°C	-65 to 175°C	-65 to 200°C
Package / Case	DO-35 (DO-204AH)	DO-7 (DO-204AA)	DO-35 (DO-204AH)	DO-7 (DO-204AA)	DO-35 (DO-204AH)
Product Status	Obsolete	Active	Active	Active	Active
RoHS Status	Not specified	Non-compliant	Not specified	Not specified	ROHS3 Compliant

Engineering Selection Recommendations

Direct Package Equivalents (DO-35):

The 1N972B-1 and 1N5256B TR PBFREE are direct mechanical and electrical substitutes for the 1N972B_T50R, both utilizing the DO-35 package. The 1N972B-1 maintains ±5% tolerance matching the original specification. The 1N5256B TR PBFREE offers ROHS3 compliance and extended temperature operation to 200°C, matching the original operating range. Both parts are currently in active production status.

Alternative Package Equivalents (DO-7):

The 1N972A and 1N972BE3 provide electrical equivalence with alternative DO-7 packaging. The 1N972A operates with ±10% tolerance, representing a relaxed specification compared to the original ±5%. The 1N972BE3 maintains ±5% tolerance. Both require PCB layout modification to accommodate the different axial package form factor. Operating temperature is limited to 175°C maximum.

Compliance Considerations:

The 1N5256B TR PBFREE is the only substitute with explicit ROHS3 compliance certification. Applications requiring RoHS compliance should prioritize this part. All substitute parts maintain REACH Unaffected status consistent with the original component.

Frequently Asked Questions (FAQ)

Q: Can the 1N972A substitute for the 1N972B_T50R in all applications?

A: The 1N972A matches the 30 V nominal Zener voltage and 500 mW power rating. However, it operates with ±10% tolerance versus the original ±5%, and uses a DO-7 package instead of DO-35. Applications sensitive to voltage tolerance or requiring DO-35 form factor should use alternative substitutes. Operating temperature is also limited to 175°C versus the original 200°C maximum.

Q: What is the difference between the 1N972B-1 and 1N5256B TR PBFREE?

A: Both parts use the DO-35 package and maintain ±5% tolerance. The 1N972B-1 is manufactured by Microchip Technology, while the 1N5256B TR PBFREE is manufactured by Central Semiconductor Corp. The 1N5256B TR PBFREE offers ROHS3 compliance and lower reverse leakage current (100 nA versus 500 nA). The 1N5256B TR PBFREE also maintains the full -65°C to 200°C operating temperature range of the original part.

Q: Are DO-35 and DO-7 packages interchangeable?

A: DO-35 and DO-7 are different axial package form factors. While both are through-hole components with similar lead spacing, they have different physical dimensions. PCB layouts designed for DO-35 require modification to accommodate DO-7 components. Mechanical fit and thermal considerations may differ between packages.

Q: Which substitute part should be selected for new designs?

A: The 1N5256B TR PBFREE is recommended for new designs due to active product status, ROHS3 compliance, and full operating temperature range matching the original specification. The 1N972B-1 is an alternative if ROHS compliance is not required and Microchip Technology sourcing is preferred.

Q: Does the 1N972B-1 have lower reverse leakage than the original part?

A: Yes. The 1N972B-1 specifies 500 nA reverse leakage at 21 V, compared to 5 µA at 22.8 V for the 1N972B_T50R. This represents significantly lower leakage current, which may affect circuit behavior in applications sensitive to reverse leakage characteristics.

Q: What is the impact of the ±10% tolerance on the 1N972A?

A: The ±10% tolerance on the 1N972A results in a Zener voltage range of 27 V to 33 V, compared to 28.5 V to 31.5 V for the ±5% specification. Applications requiring precise voltage regulation within ±5% should not use the 1N972A without circuit redesign to accommodate the wider tolerance band.

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