MMSZ5251B Zener Diode Equivalent & Substitute Parts

Part Overview

The MMSZ5251B is a 22 V, 500 mW Zener diode manufactured by onsemi in SOD-123 surface mount packaging. This component is classified as obsolete, necessitating identification of active equivalent and substitute parts for new designs and ongoing production requirements. The MMSZ5251B serves voltage regulation and transient protection applications requiring precise 22 V zener characteristics with ±5% tolerance and 500 mW power dissipation capability.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	22	V
Tolerance	±5%	—
Power - Max	500	mW
Impedance (Max)	29	Ohms
Current - Reverse Leakage @ Vr	100 nA @ 17 V	—
Voltage - Forward (Vf) (Max) @ If	900 mV @ 10 mA	—
Operating Temperature	-55°C to 150°C	—
Mounting Type	Surface Mount	—
Package / Case	SOD-123	—

Substitute Part Grouping Explanation

Substitution of the MMSZ5251B is determined by the following critical parameters: nominal zener voltage (22 V), tolerance (±5%), maximum power dissipation (500 mW), impedance characteristics, reverse leakage current, forward voltage drop, operating temperature range (-55°C to 150°C), and surface mount SOD-123 packaging.

Substitute parts are grouped into the following categories:

Direct Equivalents (onsemi MMSZ Series): Parts maintaining identical electrical specifications including 22 V nominal voltage, ±5% tolerance, 500 mW power rating, 29 Ohms impedance, and 100 nA reverse leakage at 17 V. These parts differ only in packaging format (Tape & Reel versus Cut Tape) and product status (Active versus Obsolete).

Parametric Equivalents (onsemi Automotive Grade): Parts with identical core electrical specifications but qualified to AEC-Q101 automotive standards. These include the SZMMSZ5251BT1G and SZMMSZ5251ET1G, which maintain 22 V, ±5%, 500 mW, 29 Ohms impedance, and 100 nA reverse leakage characteristics.

Direct Manufacturer Alternatives (onsemi MMSZ22 Series): Parts with matching 22 V, ±5%, 500 mW specifications but differing impedance (55 Ohms) and reverse leakage (50 nA @ 15.4 V). These include MMSZ22T1G and SZMMSZ22T1G.

Alternative Manufacturer Equivalents: Parts from Central Semiconductor Corp (CMHZ5251B TR PBFREE) and Diodes Incorporated (MMSZ5251B-7-F) maintaining identical 22 V, ±5%, 500 mW, 29 Ohms, and 100 nA specifications with extended temperature ranges.

Similar Parts (Lower Power Rating): The BZT52C22S-7-F from Diodes Incorporated provides 22 V zener voltage but with reduced 200 mW power rating and SOD-323 packaging, suitable only for applications with lower power requirements.

Similar Parts (Reduced Power Rating, Alternative Package): The BZT52H-C22,115 from Nexperia USA Inc. provides 22 V zener voltage with 375 mW power rating and SOD-123F packaging, suitable for applications tolerating lower power dissipation.

Parameter Comparison

Part Number	Manufacturer	Vz (Nom)	Tolerance	Power (Max)	Impedance (Max)	Reverse Leakage @ Vr	Vf (Max) @ If	Temp Range	Package	Status
MMSZ5251B	onsemi	22 V	±5%	500 mW	29 Ω	100 nA @ 17 V	900 mV @ 10 mA	-55°C to 150°C	SOD-123	Obsolete
MMSZ22T1G	onsemi	22 V	±5%	500 mW	55 Ω	50 nA @ 15.4 V	900 mV @ 10 mA	-55°C to 150°C	SOD-123	Active
MMSZ4708T1G	onsemi	22 V	±5%	500 mW	—	10 nA @ 16.7 V	900 mV @ 10 mA	-55°C to 150°C	SOD-123	Active
MMSZ5251BT1G	onsemi	22 V	±5%	500 mW	29 Ω	100 nA @ 17 V	900 mV @ 10 mA	-55°C to 150°C	SOD-123	Active
SZMMSZ22T1G	onsemi	22 V	±5%	500 mW	55 Ω	50 nA @ 15.4 V	900 mV @ 10 mA	-55°C to 150°C	SOD-123	Active
SZMMSZ5251BT1G	onsemi	22 V	±5%	500 mW	29 Ω	100 nA @ 17 V	900 mV @ 10 mA	-55°C to 150°C	SOD-123	Active
SZMMSZ5251ET1G	onsemi	22 V	±5%	500 mW	29 Ω	100 nA @ 17 V	900 mV @ 10 mA	-55°C to 150°C	SOD-123	Active
CMHZ5251B TR PBFREE	Central Semiconductor Corp	22 V	±5%	500 mW	29 Ω	100 nA @ 17 V	900 mV @ 10 mA	—	SOD-123	Active
MMSZ5251B-7-F	Diodes Incorporated	22 V	±5%	500 mW	29 Ω	100 nA @ 17 V	900 mV @ 10 mA	-65°C to 150°C	SOD-123	Active
BZT52C22S-7-F	Diodes Incorporated	22 V	±6%	200 mW	55 Ω	100 nA @ 15.4 V	900 mV @ 10 mA	-65°C to 150°C	SOD-323	Active
BZT52H-C22,115	Nexperia USA Inc.	22 V	±5%	375 mW	25 Ω	50 nA @ 15.4 V	900 mV @ 10 mA	-65°C to 150°C	SOD-123F	Active

Engineering Selection Recommendations

Primary Recommendation for Direct Replacement:

The MMSZ5251BT1G (onsemi) is the direct functional equivalent of the obsolete MMSZ5251B. This part maintains identical electrical specifications: 22 V nominal zener voltage, ±5% tolerance, 500 mW power dissipation, 29 Ohms impedance, and 100 nA reverse leakage at 17 V. The MMSZ5251BT1G is Active status and available in Cut Tape & Digi-Reel packaging. RoHS3 compliance is confirmed.

Automotive-Grade Alternative:

For applications requiring automotive qualification, the SZMMSZ5251BT1G and SZMMSZ5251ET1G (onsemi) provide identical electrical specifications with AEC-Q101 qualification. Both parts maintain 22 V, ±5%, 500 mW, 29 Ohms impedance, and 100 nA reverse leakage characteristics. These parts are Active status and RoHS3 compliant.

Alternative Manufacturer Equivalent:

The MMSZ5251B-7-F (Diodes Incorporated) provides identical electrical specifications with extended operating temperature range (-65°C to 150°C versus -55°C to 150°C). This part is Active status, RoHS3 compliant, and available in Cut Tape & Digi-Reel packaging.

Secondary Alternative (onsemi MMSZ22 Series):

The MMSZ22T1G and SZMMSZ22T1G (onsemi) provide 22 V, ±5%, 500 mW specifications but with increased impedance (55 Ohms versus 29 Ohms) and reduced reverse leakage (50 nA @ 15.4 V versus 100 nA @ 17 V). These parts are suitable for applications where impedance variation is acceptable. Both are Active status and RoHS3 compliant.

Lower Power Alternative (Reduced Dissipation Applications):

The BZT52H-C22,115 (Nexperia USA Inc.) provides 22 V zener voltage with reduced 375 mW power rating in SOD-123F packaging. This part is suitable only for applications with lower power dissipation requirements. AEC-Q101 automotive qualification is available. Extended temperature range (-65°C to 150°C) is provided.

Not Recommended for Direct Replacement:

The BZT52C22S-7-F (Diodes Incorporated) provides 22 V zener voltage but with significantly reduced 200 mW power rating and SOD-323 packaging. This part is suitable only for applications with substantially lower power requirements and is not a direct replacement for 500 mW applications.

Frequently Asked Questions (FAQ)

Q: Can MMSZ22T1G be used as a direct replacement for MMSZ5251B?

A: The MMSZ22T1G provides identical 22 V, ±5%, 500 mW specifications but differs in impedance (55 Ohms versus 29 Ohms) and reverse leakage characteristics (50 nA @ 15.4 V versus 100 nA @ 17 V). Substitution is permissible only if circuit design tolerates these impedance and leakage variations.

Q: What is the difference between MMSZ5251BT1G and SZMMSZ5251BT1G?

A: Both parts maintain identical electrical specifications: 22 V, ±5%, 500 mW, 29 Ohms impedance, and 100 nA reverse leakage. The SZMMSZ5251BT1G includes AEC-Q101 automotive qualification and is designated for automotive applications. The MMSZ5251BT1G is standard industrial grade.

Q: Is the MMSZ5251B-7-F from Diodes Incorporated compatible with the MMSZ5251B?

A: Yes. The MMSZ5251B-7-F maintains identical electrical specifications: 22 V, ±5%, 500 mW, 29 Ohms impedance, and 100 nA reverse leakage. The part offers extended operating temperature range (-65°C to 150°C) and is Active status with RoHS3 compliance.

Q: Why is BZT52C22S-7-F listed as a similar part rather than a direct substitute?

A: The BZT52C22S-7-F provides 22 V zener voltage but with reduced 200 mW power rating (versus 500 mW) and SOD-323 packaging (versus SOD-123). This part is suitable only for applications with lower power dissipation requirements and cannot replace the MMSZ5251B in 500 mW applications.

Q: What packaging formats are available for MMSZ5251B equivalents?

A: The MMSZ5251BT1G is available in Cut Tape & Digi-Reel packaging. The MMSZ22T1G, MMSZ4708T1G, SZMMSZ22T1G, SZMMSZ5251BT1G, and SZMMSZ5251ET1G are available in Tape & Reel format. The CMHZ5251B TR PBFREE is available in Tape & Reel format. Packaging selection depends on production volume and assembly requirements.

Q: Are all substitute parts RoHS3 compliant?

A: All Active status substitute parts listed are RoHS3 compliant. The CMHZ5251B TR PBFREE is explicitly marked as lead-free. Compliance documentation should be verified with the component supplier for specific production lots.

Q: Can MMSZ4708T1G be used as a replacement for MMSZ5251B?

A: The MMSZ4708T1G provides 22 V, ±5%, 500 mW specifications with superior reverse leakage characteristics (10 nA @ 16.7 V versus 100 nA @ 17 V). Impedance specification is not provided for this part. Substitution is permissible if impedance variation is acceptable and lower leakage current is beneficial to circuit performance.

Q: What is the significance of the automotive-grade SZMMSZ parts?

A: The SZMMSZ5251BT1G and SZMMSZ5251ET1G include AEC-Q101 automotive qualification, indicating compliance with automotive reliability and quality standards. These parts are required for automotive applications and provide identical electrical specifications to the standard MMSZ5251BT1G.

Q: Is the CMHZ5251B TR PBFREE from Central Semiconductor Corp a suitable alternative?

A: Yes. The CMHZ5251B TR PBFREE maintains identical electrical specifications: 22 V, ±5%, 500 mW, 29 Ohms impedance, and 100 nA reverse leakage. This part is Active status, RoHS3 compliant, and lead-free. Operating temperature range specification is limited to 150°C maximum.

Request Quote (Ships tomorrow)

Part Number

Quantity

Company

Contact Name

E-mail

Message