MMSZ5257B Zener Diode 33V 500mW SOD-123 Equivalent & Substitute Parts

Part Overview

The MMSZ5257B is a 33 V, 500 mW Zener diode in SOD-123 surface mount packaging manufactured by onsemi. This component is classified as obsolete, though 24,200 units remain in stock. The MMSZ5257B serves as a voltage regulation and transient protection element in electronic circuits requiring 33 V nominal Zener voltage with ±5% tolerance and surface mount integration.

Due to its obsolete product status, direct replacement with active production equivalents is necessary for new designs and long-term supply chain continuity. Multiple substitute options exist within the onsemi product portfolio, offering identical or superior electrical characteristics while maintaining active production status and enhanced compliance certifications.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	33	V
Tolerance	±5	%
Power - Max	500	mW
Impedance (Max)	58	Ohms
Current - Reverse Leakage @ Vr	100 nA @ 25 V	nA
Voltage - Forward (Vf) (Max) @ If	900 mV @ 10 mA	mV
Operating Temperature Range	-55 to 150	°C
Mounting Type	Surface Mount
Package / Case	SOD-123
Moisture Sensitivity Level	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution of the MMSZ5257B is determined by strict equivalence across the following critical parameters:

Primary Substitution Criteria:

Voltage - Zener (Nom): 33 V
Tolerance: ±5%
Power - Max: 500 mW
Voltage - Forward (Vf) (Max) @ If: 900 mV @ 10 mA
Operating Temperature Range: -55°C to 150°C
Mounting Type: Surface Mount
Package / Case: SOD-123

Secondary Compatibility Parameters:

Impedance (Max) (Zzt): 58 Ohms (primary specification) or 80 Ohms (acceptable variance)
Current - Reverse Leakage @ Vr: 100 nA @ 25 V (primary) or 50 nA @ 23.1 V (improved performance) or 10 nA @ 25 V (superior performance)

Substitute parts are grouped into three categories based on electrical equivalence and product status:

Direct Manufacturer Equivalents (Active Production): Parts with identical electrical specifications and active product status, available in standard packaging configurations.
Automotive-Grade Equivalents (AEC-Q101 Qualified): Parts meeting automotive qualification standards with identical electrical specifications, suitable for applications requiring automotive-grade reliability.
Parametric Equivalents (Enhanced Performance): Parts with superior reverse leakage characteristics or equivalent impedance specifications, maintaining full electrical compatibility.

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance (%)	Power (mW)	Zzt (Ohms)	Reverse Leakage @ Vr	Vf (Max) @ If	Temp Range (°C)	Package	Product Status	RoHS	Automotive Grade
MMSZ5257B	onsemi	33	±5	500	58	100 nA @ 25 V	900 mV @ 10 mA	-55 to 150	SOD-123	Obsolete	Not Specified	No
MMSZ33T1G	onsemi	33	±5	500	80	50 nA @ 23.1 V	900 mV @ 10 mA	-55 to 150	SOD-123	Active	ROHS3	No
MMSZ4714T1G	onsemi	33	±5	500	Not Specified	10 nA @ 25 V	900 mV @ 10 mA	-55 to 150	SOD-123	Active	ROHS3	No
MMSZ5257BT1G	onsemi	33	±5	500	58	100 nA @ 25 V	900 mV @ 10 mA	-55 to 150	SOD-123	Active	ROHS3	No
MMSZ5257ET1G	onsemi	33	±5	500	58	100 nA @ 25 V	900 mV @ 10 mA	-55 to 150	SOD-123	Active	ROHS3	No
SZMMSZ33T1G	onsemi	33	±5	500	80	50 nA @ 23.1 V	900 mV @ 10 mA	-55 to 150	SOD-123	Active	ROHS3	Yes (AEC-Q101)
SZMMSZ33ET1G	onsemi	33	±5	500	80	50 nA @ 23.1 V	900 mV @ 10 mA	-55 to 150	SOD-123	Active	ROHS3	Yes (AEC-Q101)
SZMMSZ33ET3G	onsemi	33	±5	500	80	50 nA @ 23.1 V	900 mV @ 10 mA	-55 to 150	SOD-123	Active	ROHS3	Yes (AEC-Q101)
SZMMSZ4714T1G	onsemi	33	Not Specified	500	Not Specified	10 nA @ 25 V	900 mV @ 10 mA	-55 to 150	SOD-123	Active	ROHS3	Yes (AEC-Q101)
SZMMSZ5257BT1G	onsemi	33	±5	500	58	100 nA @ 25 V	900 mV @ 10 mA	-55 to 150	SOD-123	Active	ROHS3	Yes (AEC-Q101)
SZMMSZ5257ET1G	onsemi	33	±5	500	58	100 nA @ 25 V	900 mV @ 10 mA	-55 to 150	SOD-123	Active	ROHS3	Yes (AEC-Q101)

Engineering Selection Recommendations

For Standard Industrial Applications:

MMSZ5257BT1G and MMSZ5257ET1G are direct functional replacements for MMSZ5257B. Both parts maintain identical electrical specifications including 33 V nominal Zener voltage, ±5% tolerance, 500 mW power rating, and 58 Ohms maximum impedance. Both are in active production status with ROHS3 compliance. MMSZ5257BT1G is available in Tape & Reel packaging with 38,300 units in stock. MMSZ5257ET1G is available in Tape & Reel packaging with 37,637 units in stock.

For Applications Requiring Improved Reverse Leakage Performance:

MMSZ4714T1G provides superior reverse leakage characteristics at 10 nA @ 25 V compared to the MMSZ5257B specification of 100 nA @ 25 V. This part maintains all other electrical parameters including 33 V nominal Zener voltage, ±5% tolerance, and 500 mW power rating. MMSZ4714T1G is in active production with ROHS3 compliance and 2,680 units in stock.

For Automotive Applications Requiring AEC-Q101 Qualification:

SZMMSZ5257BT1G and SZMMSZ5257ET1G are automotive-grade equivalents with AEC-Q101 qualification. Both maintain identical electrical specifications to MMSZ5257B including 33 V nominal Zener voltage, ±5% tolerance, 500 mW power rating, and 58 Ohms maximum impedance. SZMMSZ5257BT1G is available with 53,400 units in stock. SZMMSZ5257ET1G is available with 4,035 units in stock. Both are ROHS3 compliant and in active production.

For Automotive Applications with Improved Reverse Leakage:

SZMMSZ4714T1G provides automotive-grade AEC-Q101 qualification with superior reverse leakage at 10 nA @ 25 V. This part maintains 33 V nominal Zener voltage and 500 mW power rating. SZMMSZ4714T1G is in active production with ROHS3 compliance and 5,796 units in stock.

For Applications with Relaxed Impedance Tolerance:

MMSZ33T1G and SZMMSZ33T1G accept 80 Ohms maximum impedance compared to the MMSZ5257B specification of 58 Ohms. Both maintain 33 V nominal Zener voltage, ±5% tolerance, and 500 mW power rating. MMSZ33T1G is available with 1,412 units in stock. SZMMSZ33T1G is automotive-grade AEC-Q101 qualified and available with 6,100 units in stock.

Frequently Asked Questions (FAQ)

Q: Can MMSZ5257BT1G directly replace MMSZ5257B in existing designs?

A: Yes. MMSZ5257BT1G maintains identical electrical specifications including 33 V nominal Zener voltage, ±5% tolerance, 500 mW power rating, 58 Ohms maximum impedance, and 900 mV forward voltage at 10 mA. Both operate across -55°C to 150°C and use SOD-123 surface mount packaging. The primary difference is product status: MMSZ5257B is obsolete while MMSZ5257BT1G is in active production with ROHS3 compliance.

Q: What is the difference between MMSZ5257BT1G and MMSZ5257ET1G?

A: Both parts are electrically identical with 33 V nominal Zener voltage, ±5% tolerance, 500 mW power rating, and 58 Ohms maximum impedance. The difference lies in packaging configuration and inventory availability. MMSZ5257BT1G is supplied in Tape & Reel with 38,300 units in stock. MMSZ5257ET1G is supplied in Tape & Reel with 37,637 units in stock. Both are active production parts with ROHS3 compliance.

Q: When should I use SZMMSZ5257BT1G instead of MMSZ5257BT1G?

A: SZMMSZ5257BT1G is required for automotive applications requiring AEC-Q101 qualification. Both parts maintain identical electrical specifications including 33 V nominal Zener voltage, ±5% tolerance, 500 mW power rating, and 58 Ohms maximum impedance. SZMMSZ5257BT1G is automotive-grade qualified while MMSZ5257BT1G is standard industrial grade. Both are ROHS3 compliant and in active production.

Q: What is the advantage of MMSZ4714T1G over MMSZ5257BT1G?

A: MMSZ4714T1G provides superior reverse leakage performance at 10 nA @ 25 V compared to MMSZ5257BT1G at 100 nA @ 25 V. Both maintain 33 V nominal Zener voltage, ±5% tolerance, and 500 mW power rating in SOD-123 packaging. MMSZ4714T1G is suitable for applications where lower reverse leakage current is required. Both are active production parts with ROHS3 compliance.

Q: Can I use MMSZ33T1G as a substitute for MMSZ5257B?

A: MMSZ33T1G is electrically compatible with MMSZ5257B for applications where impedance tolerance is not critical. Both maintain 33 V nominal Zener voltage, ±5% tolerance, 500 mW power rating, and 900 mV forward voltage at 10 mA. MMSZ33T1G specifies 80 Ohms maximum impedance compared to MMSZ5257B at 58 Ohms. MMSZ33T1G is active production with ROHS3 compliance and 1,412 units in stock.

Q: What packaging options are available for substitute parts?

A: Substitute parts are available in Tape & Reel (TR) and Cut Tape (CT) & Digi-Reel configurations. MMSZ5257BT1G, MMSZ5257ET1G, SZMMSZ5257BT1G, and SZMMSZ5257ET1G are supplied in Tape & Reel. MMSZ4714T1G is supplied in Cut Tape & Digi-Reel. All parts use SOD-123 surface mount package with identical footprint compatibility.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All active production substitute parts listed are ROHS3 compliant. MMSZ5257B does not specify RoHS status as it is obsolete. All substitute parts maintain REACH Unaffected status and EAR99 export classification.

Q: Which substitute part has the lowest reverse leakage current?

A: MMSZ4714T1G and SZMMSZ4714T1G both specify 10 nA @ 25 V reverse leakage current, which is superior to MMSZ5257B at 100 nA @ 25 V. MMSZ4714T1G is standard industrial grade. SZMMSZ4714T1G is automotive-grade AEC-Q101 qualified.

Q: Can I mix different substitute parts in the same production run?

A: All substitute parts maintain identical 33 V nominal Zener voltage, ±5% tolerance, 500 mW power rating, and 900 mV forward voltage at 10 mA. Impedance specifications vary between 58 Ohms and 80 Ohms. Parts with identical impedance specifications (58 Ohms: MMSZ5257BT1G, MMSZ5257ET1G, SZMMSZ5257BT1G, SZMMSZ5257ET1G) are interchangeable. Parts with 80 Ohms impedance (MMSZ33T1G, SZMMSZ33T1G, SZMMSZ33ET1G, SZMMSZ33ET1G) are interchangeable with each other but not with 58 Ohms parts if impedance tolerance is critical.

Q: What is the moisture sensitivity level for substitute parts?

A: All substitute parts specify Moisture Sensitivity Level (MSL) 1 (Unlimited), indicating no moisture sensitivity restrictions. Parts can be stored and handled without special moisture control measures.

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