1N5937B Zener Diode Equivalent & Substitute Parts

Part Overview

The 1N5937B is a 33 V, 3 W axial through-hole zener diode manufactured by onsemi with ±5% voltage tolerance. This component is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production requirements. The 1N5937B operates across a temperature range of -65°C to 200°C and is housed in a DO-204AL (DO-41) axial package. Substitute parts must maintain the 33 V nominal zener voltage and through-hole axial mounting configuration while accommodating variations in power rating, tolerance, and compliance status.

Key Parameters

Parameter	1N5937B Value	Unit
Voltage - Zener (Nom)	33	V
Power - Max	3	W
Tolerance	±5%	%
Impedance (Max)	33	Ohms
Current - Reverse Leakage @ Vr	1	µA @ 25.1 V
Voltage - Forward (Vf) (Max) @ If	1.5	V @ 200 mA
Operating Temperature	-65 to 200	°C
Mounting Type	Through Hole
Package / Case	DO-204AL, DO-41, Axial

Substitute Part Grouping Explanation

Substitution of the 1N5937B is determined by the following critical parameters:

Primary Substitution Criteria:

Nominal zener voltage of 33 V
Through-hole axial mounting configuration
Compatible package types: DO-204AL (DO-41) or T-18 axial

Secondary Substitution Criteria:

Power rating equal to or greater than 3 W
Voltage tolerance compatible with circuit requirements
Operating temperature range encompassing -65°C to 200°C
Impedance characteristics within acceptable limits

Substitute parts are grouped into two categories based on power rating and package configuration:

Category 1: Direct Axial Package Substitutes (DO-204AL/DO-41) Parts maintaining the same axial package footprint with varying power ratings (1.25 W to 1.5 W) and tolerance specifications. These parts are pin-compatible and require no PCB layout modifications.

Category 2: Enhanced Performance Substitutes (T-18 Axial) Parts with increased power dissipation (5 W) in a larger T-18 axial package. These parts provide superior thermal performance and lower impedance but require verification of physical space availability on the PCB.

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Power (W)	Tolerance	Zzt (Ohms)	Vf @ If (V @ mA)	Temp Range (°C)	Package	Product Status	RoHS Status
1N5937B	onsemi	33	3	±5%	33	1.5 @ 200	-65 to 200	DO-204AL	Obsolete	Non-compliant
1N5937BRLG	onsemi	33	3	±5%	33	1.5 @ 200	-65 to 200	DO-204AL	Active	ROHS3 Compliant
1N5364BE3/TR13	Microchip Technology	33	5	±5%	10	1.2 @ 1000	-65 to 150	T-18	Active	ROHS3 Compliant
1N5364CE3/TR13	Microchip Technology	33	5	±2%	10	1.2 @ 1000	-65 to 150	T-18	Active	ROHS3 Compliant
1N5364E3/TR13	Microchip Technology	33	5	±20%	10	1.2 @ 1000	-65 to 150	T-18	Active	ROHS3 Compliant
1N5937CG	Microsemi Corporation	33	1.25	±2%	33	1.2 @ 200	-65 to 175	DO-204AL	Active	Non-compliant
1N5937DG	Microsemi Corporation	33	1.25	±1%	33	1.2 @ 200	-65 to 175	DO-204AL	Active	Non-compliant
1N5937P/TR12	Microchip Technology	33	1.5	±20%	33	1.2 @ 200	-65 to 150	DO-204AL	Active	Non-compliant
1N5937P/TR8	Microchip Technology	33	1.5	±20%	33	1.2 @ 200	-65 to 150	DO-204AL	Active	Non-compliant
1N5937PE3/TR12	Microchip Technology	33	1.5	±20%	33	1.2 @ 200	-65 to 150	DO-204AL	Active	ROHS3 Compliant
1N5937PE3/TR8	Microchip Technology	33	1.5	±20%	33	1.2 @ 200	-65 to 150	DO-204AL	Active	ROHS3 Compliant

Engineering Selection Recommendations

Primary Recommendation: 1N5937BRLG

The 1N5937BRLG is the direct functional equivalent of the 1N5937B. It maintains identical electrical specifications (33 V, 3 W, ±5% tolerance) and package configuration (DO-204AL axial). The 1N5937BRLG is in active product status and carries ROHS3 compliance certification, addressing the obsolescence of the original part while maintaining full electrical and mechanical compatibility. This part requires no circuit redesign or PCB layout modification.

Secondary Recommendation for RoHS Compliance: 1N5937PE3/TR8 or 1N5937PE3/TR12

For applications requiring RoHS3 compliance with reduced power dissipation requirements, the 1N5937PE3 series offers 1.5 W power rating in the same DO-204AL package. These parts are active and ROHS3 compliant. The reduced power rating is suitable for circuits where the full 3 W capability of the original part is not required. Both TR8 and TR12 variants are electrically identical; selection depends on tape reel configuration requirements.

Alternative for Enhanced Thermal Performance: 1N5364BE3/TR13 or 1N5364CE3/TR13

The 1N5364 series from Microchip Technology provides 5 W power dissipation in a T-18 axial package with significantly lower impedance (10 Ohms versus 33 Ohms). These parts are active and ROHS3 compliant. The 1N5364CE3/TR13 offers tighter tolerance (±2%) compared to the 1N5364BE3/TR13 (±5%). Selection of the T-18 package requires verification that physical space is available on the PCB, as this package is larger than the DO-204AL configuration.

Not Recommended: 1N5937CG and 1N5937DG

The 1N5937CG and 1N5937DG parts feature reduced power ratings (1.25 W) below the original 3 W specification. These parts are suitable only for applications where power dissipation requirements are confirmed to be below 1.25 W. Both parts are RoHS non-compliant.

Not Recommended: 1N5937P/TR12 and 1N5937P/TR8

The 1N5937P series provides 1.5 W power rating, which is below the original 3 W specification. These parts are suitable only for applications with confirmed reduced power requirements. Both variants are RoHS non-compliant.

Not Recommended: 1N5364E3/TR13

The 1N5364E3/TR13 carries a ±20% tolerance specification, which exceeds the ±5% tolerance of the original part. This part is suitable only for applications with relaxed tolerance requirements.

Frequently Asked Questions (FAQ)

Q: Can the 1N5937BRLG be used as a direct replacement for the 1N5937B?

A: Yes. The 1N5937BRLG is electrically and mechanically identical to the 1N5937B. Both parts feature 33 V nominal zener voltage, 3 W power rating, ±5% tolerance, and DO-204AL axial package configuration. The 1N5937BRLG is in active production status with ROHS3 compliance, whereas the 1N5937B is obsolete. No circuit modifications or PCB layout changes are required.

Q: What is the difference between the DO-204AL and T-18 packages?

A: Both are axial through-hole packages for zener diodes. The DO-204AL (also designated DO-41) is the standard smaller package used in the 1N5937 series. The T-18 is a larger axial package used in the 1N5364 series, providing increased physical size for enhanced thermal dissipation. The T-18 package requires verification of available PCB space before substitution.

Q: Can I use a 1.5 W part (1N5937P/TR8) instead of the original 3 W part (1N5937B)?

A: Only if the circuit design has been verified to operate with power dissipation below 1.5 W. The 1N5937B is rated for 3 W maximum power dissipation. Using a lower-rated part in a circuit requiring 3 W operation will result in component failure. Confirm actual power dissipation requirements before selecting a lower-rated substitute.

Q: What is the advantage of the 1N5364 series over the 1N5937 series?

A: The 1N5364 series provides 5 W power dissipation compared to the 1N5937B's 3 W rating, and features significantly lower impedance (10 Ohms versus 33 Ohms). The lower impedance results in improved voltage regulation characteristics. The trade-off is a larger T-18 package footprint and a reduced maximum operating temperature (150°C versus 200°C for the 1N5937B).

Q: Are all substitute parts RoHS compliant?

A: No. The 1N5937CG, 1N5937DG, 1N5937P/TR12, 1N5937P/TR8, and 1N5937B itself are RoHS non-compliant. The 1N5937BRLG, 1N5937PE3/TR12, 1N5937PE3/TR8, 1N5364BE3/TR13, 1N5364CE3/TR13, and 1N5364E3/TR13 are ROHS3 compliant. For applications requiring RoHS compliance, select from the compliant parts listed.

Q: What tolerance options are available for 33 V zener diodes?

A: The substitute parts listed offer tolerance specifications of ±1%, ±2%, ±5%, and ±20%. The original 1N5937B features ±5% tolerance. Tighter tolerances (±1% and ±2%) are available in the 1N5937DG, 1N5937CG, and 1N5364CE3/TR13 parts. Relaxed tolerance (±20%) is available in the 1N5364E3/TR13 and 1N5937P series. Select tolerance based on circuit voltage regulation requirements.

Q: What is the maximum operating temperature for each substitute part?

A: The 1N5937B operates to 200°C. The 1N5937BRLG, 1N5937CG, and 1N5937DG operate to 175°C or 200°C. The Microchip Technology 1N5364 series (all variants) operates to 150°C maximum. The Microchip Technology 1N5937P series operates to 150°C maximum. For applications requiring operation above 150°C, select the 1N5937BRLG or Microsemi parts.

Q: Can I substitute a higher power-rated part in a circuit designed for the 1N5937B?

A: Yes. Substituting a higher power-rated part (such as the 5 W 1N5364 series) is electrically acceptable and provides improved thermal margin. However, physical package size must be verified. The T-18 package used in the 1N5364 series is larger than the DO-204AL package of the 1N5937B and may not fit the existing PCB footprint without layout modification.

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