BZX79C51 Equivalent & Substitute Parts

Part Overview

The BZX79C51 is a 51 V, 500 mW Zener diode manufactured by onsemi in DO-35 through-hole axial package. This component is classified as obsolete, indicating that onsemi has discontinued production. Equivalent and substitute parts are necessary to maintain design continuity, ensure supply chain availability, and support ongoing production requirements for applications utilizing this Zener diode specification.

Key Parameters

Parameter	Value
Voltage - Zener (Nom)	51 V
Tolerance	±5%
Power - Max	500 mW
Impedance (Max)	180 Ohms
Current - Reverse Leakage @ Vr	500 nA @ 35.7 V
Voltage - Forward (Vf) (Max) @ If	1.5 V @ 100 mA
Operating Temperature	-65°C ~ 200°C
Mounting Type	Through Hole
Package / Case	DO-204AH, DO-35, Axial

Substitute Part Grouping Explanation

Substitution of the BZX79C51 is determined by the following critical parameters:

Primary Substitution Criteria:

Zener voltage: 51 V nominal
Tolerance: ±5% or tighter
Power dissipation: 500 mW or greater
Impedance (Max): 180 Ohms or lower
Operating temperature range: -65°C to 200°C or equivalent
Mounting type: Through Hole
Package compatibility: DO-35 or equivalent axial package

Direct Substitutes maintain all electrical parameters within the specified tolerances and use identical or functionally equivalent packaging.

Similar Substitutes meet the core electrical requirements (51 V nominal, ±5% tolerance, 500 mW power rating) but may have minor variations in secondary parameters such as impedance, reverse leakage current, or forward voltage characteristics. These parts are suitable for applications where the primary electrical specifications are the controlling factors.

Higher Power Alternatives exceed the 500 mW power rating, providing additional thermal margin and are applicable in designs where increased power dissipation capability is beneficial or required.

Parameter Comparison

Part Number	Manufacturer	Vz (Nom)	Tolerance	Power (Max)	Zzt (Max)	Vf (Max) @ If	Temp Range	Package	Status
BZX79C51	onsemi	51 V	±5%	500 mW	180 Ω	1.5 V @ 100 mA	-65°C ~ 200°C	DO-35	Obsolete
1N5369BRLG	onsemi	51 V	±5%	5 W	27 Ω	1.2 V @ 1 A	-65°C ~ 200°C	Axial	Active
BZX79-C51,113	Nexperia USA Inc.	51 V	±5%	400 mW	180 Ω	900 mV @ 10 mA	-65°C ~ 200°C	DO-35	Active
BZX79-C51,143	Nexperia USA Inc.	51 V	±5%	400 mW	180 Ω	900 mV @ 10 mA	-65°C ~ 200°C	DO-35	Active
1N5262BDO35	Microsemi Corporation	51 V	±5%	500 mW	125 Ω	1.5 V @ 200 mA	-65°C ~ 175°C	DO-35	Active
1N5753B	Microchip Technology	51 V	±5%	500 mW	180 Ω	900 mV @ 10 mA	-65°C ~ 175°C	DO-35	Active
1N5753C	Microchip Technology	51 V	±1%	500 mW	180 Ω	900 mV @ 10 mA	-65°C ~ 175°C	DO-35	Active
1N5753D	Microchip Technology	51 V	±1%	500 mW	180 Ω	900 mV @ 10 mA	-65°C ~ 175°C	DO-35	Active
1N6017A	Microchip Technology	51 V	±10%	500 mW	225 Ω	1.1 V @ 200 mA	-65°C ~ 175°C	DO-35	Active
1N6017B	Microchip Technology	51 V	±5%	500 mW	180 Ω	1.1 V @ 200 mA	-65°C ~ 175°C	DO-35	Active
1N6017C	Microchip Technology	51 V	±2%	500 mW	180 Ω	1.1 V @ 200 mA	-65°C ~ 175°C	DO-35	Active

Engineering Selection Recommendations

Direct Substitutes (Highest Compatibility):

The BZX79-C51,113 and BZX79-C51,143 from Nexperia USA Inc. are direct substitutes with active product status and ROHS3 compliance. Both parts maintain the 51 V nominal voltage, ±5% tolerance, and DO-35 package. The 400 mW power rating is lower than the original 500 mW specification; however, this reduction is acceptable for applications operating below 400 mW dissipation levels. Both parts feature identical impedance (180 Ω) and operating temperature range (-65°C to 200°C) as the BZX79C51. The primary difference is packaging format: BZX79-C51,113 is supplied in Tape & Reel, while BZX79-C51,143 is supplied in Tape & Box.

Equivalent Substitutes (Electrical Compatibility):

The 1N5753B, 1N5753C, and 1N5753D from Microchip Technology are electrically equivalent with 51 V nominal voltage, 500 mW power rating, and DO-35 packaging. The 1N5753C and 1N5753D offer tighter tolerance (±1%) compared to the original ±5% specification. All three parts are active products. The operating temperature range extends to 175°C maximum, which is 25°C lower than the BZX79C51. These parts are suitable for applications where the upper temperature limit does not exceed 175°C.

The 1N5262BDO35 from Microsemi Corporation matches the 51 V, ±5% tolerance, 500 mW power rating, and DO-35 package. This part features lower impedance (125 Ω) and is active. The operating temperature range is -65°C to 175°C.

The 1N6017B from Microchip Technology provides 51 V nominal voltage, ±5% tolerance, 500 mW power rating, and DO-35 package with active status. The operating temperature range is -65°C to 175°C.

Higher Power Alternative:

The 1N5369BRLG from onsemi is a higher power variant rated at 5 W with 51 V nominal voltage and ±5% tolerance. This part is active and maintains the full -65°C to 200°C operating temperature range. The significantly lower impedance (27 Ω) and higher power rating make this suitable for applications requiring increased thermal margin or higher current handling capability.

Tolerance Considerations:

Applications requiring tighter voltage tolerance should specify 1N5753C or 1N5753D (±1% tolerance) or 1N6017C (±2% tolerance). Applications with relaxed tolerance requirements may use 1N6017A (±10% tolerance).

Compliance Status:

Nexperia parts (BZX79-C51,113 and BZX79-C51,143) carry ROHS3 compliance certification. Microchip and Microsemi parts are marked as RoHS non-compliant. Selection should account for end-product compliance requirements.

Frequently Asked Questions (FAQ)

Q: Can the BZX79-C51,113 replace the BZX79C51 in all applications?

A: The BZX79-C51,113 is a direct substitute for applications where power dissipation does not exceed 400 mW. The part maintains identical voltage (51 V), tolerance (±5%), impedance (180 Ω), and operating temperature range (-65°C to 200°C). If the application requires the full 500 mW power rating, alternative parts with higher power ratings should be selected.

Q: What is the difference between 1N5753B, 1N5753C, and 1N5753D?

A: All three parts share identical electrical specifications: 51 V nominal voltage, 500 mW power rating, 180 Ω impedance, and DO-35 package. The primary difference is voltage tolerance: 1N5753B has ±5% tolerance, while 1N5753C and 1N5753D both have ±1% tolerance. Selection depends on the application's tolerance requirements.

Q: Is the 1N5369BRLG suitable as a direct replacement?

A: The 1N5369BRLG is electrically compatible with the BZX79C51 for the core function (51 V Zener regulation). However, the 5 W power rating and significantly lower impedance (27 Ω) represent a substantial upgrade. This part is suitable for applications where increased power dissipation capability is beneficial. The axial package format is compatible with through-hole mounting. Verify that the higher power rating and lower impedance do not introduce unintended circuit behavior in the specific application.

Q: What is the impact of operating temperature range differences?

A: The BZX79C51 operates from -65°C to 200°C. Microchip and Microsemi alternatives operate from -65°C to 175°C, a 25°C reduction at the upper limit. Applications operating above 175°C require the BZX79C51 or the 1N5369BRLG (which maintains the full -65°C to 200°C range). For applications with maximum operating temperatures at or below 175°C, the reduced range does not present a limitation.

Q: Are there RoHS compliance differences between substitute options?

A: Yes. The Nexperia parts (BZX79-C51,113 and BZX79-C51,143) are ROHS3 compliant. The Microchip Technology and Microsemi Corporation parts are marked as RoHS non-compliant. End-product RoHS compliance requirements determine which substitute parts are acceptable.

Q: Can I use 1N6017A in place of BZX79C51?

A: The 1N6017A is electrically compatible with 51 V nominal voltage and 500 mW power rating in DO-35 package. However, the ±10% tolerance is significantly looser than the original ±5% specification, and the impedance is higher (225 Ω versus 180 Ω). This part is suitable only for applications with relaxed voltage tolerance requirements.

Q: What packaging differences exist between substitute parts?

A: The BZX79C51 uses DO-35 axial through-hole package. All listed substitute parts maintain DO-35 or equivalent axial through-hole packaging, ensuring mechanical compatibility. Packaging format variations (Tape & Reel, Tape & Box, Bulk) affect supply and handling but do not impact electrical performance or board-level compatibility.

Q: How do impedance differences affect circuit performance?

A: Impedance (Zzt) affects the dynamic resistance of the Zener diode. Lower impedance provides better voltage regulation under varying load conditions. The BZX79C51 has 180 Ω impedance. The 1N5262BDO35 has lower impedance (125 Ω), providing superior regulation. The 1N6017A has higher impedance (225 Ω), resulting in less precise regulation. Select based on the application's voltage regulation requirements.

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