MMSZ5248B-7 Equivalent & Substitute Parts

Part Overview

The MMSZ5248B-7 is an 18 V, 500 mW Zener diode manufactured by Diodes Incorporated in SOD-123 surface mount packaging. This part is discontinued at DiGi Electronics, making equivalent and substitute parts necessary for ongoing design support and production continuity. The device operates across a temperature range of -65°C to 150°C with ±5% voltage tolerance and is classified as RoHS non-compliant.

Substitute parts are identified based on matching or exceeding the core electrical specifications: 18 V nominal Zener voltage, surface mount SOD-123 package compatibility, and operating temperature range. Alternatives include direct replacements from the same manufacturer, functionally equivalent parts from other manufacturers, and parts with enhanced specifications or compliance certifications.

Key Parameters

Parameter	MMSZ5248B-7 Specification
Voltage - Zener (Nom)	18 V
Tolerance	±5%
Power - Max	500 mW
Impedance (Max)	21 Ohms
Current - Reverse Leakage @ Vr	100 nA @ 14 V
Voltage - Forward (Vf) (Max) @ If	900 mV @ 10 mA
Operating Temperature	-65°C ~ 150°C
Mounting Type	Surface Mount
Package / Case	SOD-123
RoHS Status	RoHS non-compliant
Moisture Sensitivity Level	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution logic for the MMSZ5248B-7 is based on the following critical parameters:

Primary Matching Criteria:

Nominal Zener voltage: 18 V
Package type: SOD-123 or SOD-123F surface mount
Operating temperature range: minimum -65°C to 150°C
Mounting type: Surface Mount

Secondary Compatibility Factors:

Power dissipation: 500 mW or greater
Voltage tolerance: ±5% or tighter
Impedance: 21 Ohms or lower preferred for circuit stability
Reverse leakage current: 100 nA @ 14 V or lower

Substitute parts are grouped into three categories:

Direct Manufacturer Replacement: Same manufacturer (Diodes Incorporated) with identical electrical specifications and improved packaging or compliance status.
Functionally Equivalent Alternatives: Different manufacturers with matching 18 V Zener voltage, SOD-123 package, and compatible operating temperature range. These parts may have different power ratings, impedance values, or tolerance specifications but remain electrically interchangeable within circuit design parameters.
Enhanced Specification Alternatives: Parts with superior electrical characteristics (lower impedance, tighter tolerance, lower leakage current) or additional certifications (RoHS3 compliance, AEC-Q101 automotive qualification) that provide design flexibility and regulatory compliance.

Parameter Comparison

Part Number	Manufacturer	Vz (Nom)	Tolerance	Power (Max)	Zzt (Max)	Package	Temp Range	RoHS Status	Product Status
MMSZ5248B-7	Diodes Incorporated	18 V	±5%	500 mW	21 Ω	SOD-123	-65°C ~ 150°C	Non-compliant	Discontinued
MMSZ5248B-7-F	Diodes Incorporated	18 V	±5%	500 mW	21 Ω	SOD-123	-65°C ~ 150°C	ROHS3 Compliant	Active
BZT52B18-E3-08	Vishay General Semiconductor	18 V	±2%	410 mW	45 Ω	SOD-123	-65°C ~ 150°C	ROHS3 Compliant	Active
BZT52B18-E3-18	Vishay General Semiconductor	18 V	±2%	410 mW	45 Ω	SOD-123	-65°C ~ 150°C	ROHS3 Compliant	Active
BZT52B18-TP	Micro Commercial Co	18 V	±2%	410 mW	50 Ω	SOD-123	-55°C ~ 175°C	ROHS3 Compliant	Active
BZT52C18-G3-08	Vishay General Semiconductor	18 V	±5%	410 mW	45 Ω	SOD-123	-55°C ~ 150°C	ROHS3 Compliant	Active
BZT52C18-TP	Micro Commercial Co	18 V	±6%	200 mW	45 Ω	SOD-123	-65°C ~ 150°C	ROHS3 Compliant	Active
BZT52H-C18,115	Nexperia USA Inc.	18 V	±5%	375 mW	20 Ω	SOD-123F	-65°C ~ 150°C	ROHS3 Compliant	Active
MMSZ18ET1G	onsemi	18 V	±5%	500 mW	45 Ω	SOD-123	-55°C ~ 150°C	ROHS3 Compliant	Active
MMSZ18T1G	onsemi	18 V	±5%	500 mW	45 Ω	SOD-123	-55°C ~ 150°C	ROHS3 Compliant	Active
MMSZ4705-HE3-08	Vishay General Semiconductor	18 V	±5%	500 mW	—	SOD-123	-55°C ~ 150°C	ROHS3 Compliant	Obsolete

Engineering Selection Recommendations

Primary Recommendation: MMSZ5248B-7-F

The MMSZ5248B-7-F is the direct equivalent replacement from Diodes Incorporated. It maintains identical electrical specifications (18 V, 500 mW, ±5% tolerance, 21 Ω impedance) and operating temperature range (-65°C to 150°C) as the original MMSZ5248B-7. The primary advantage is ROHS3 compliance status and active product availability with substantial inventory (77,400 units). This part is suitable for designs requiring no circuit modifications and is the preferred choice for direct substitution.

Secondary Recommendations for RoHS3 Compliance:

For applications requiring RoHS3 compliance with maintained power dissipation:

MMSZ18T1G (onsemi): Matches 18 V, 500 mW, ±5% tolerance specifications with SOD-123 package. Operating temperature range is -55°C to 150°C (narrower low-temperature range). Impedance is 45 Ω (higher than original). Extensive inventory availability (155,400 units in Cut Tape packaging).
MMSZ18ET1G (onsemi): Identical specifications to MMSZ18T1G with Tape & Reel packaging option. Suitable for automated assembly processes.

Alternative Recommendations for Reduced Power Dissipation Applications:

For circuits tolerating lower power ratings:

BZT52B18-E3-08 or BZT52B18-E3-18 (Vishay): 18 V, 410 mW, ±2% tolerance (tighter than original). Operating temperature -65°C to 150°C. Impedance 45 Ω. ROHS3 compliant. Tighter tolerance specification provides improved voltage regulation characteristics.
BZT52C18-G3-08 (Vishay): 18 V, 410 mW, ±5% tolerance, 45 Ω impedance. Operating temperature -55°C to 150°C. ROHS3 compliant. Suitable for applications not requiring extended low-temperature operation below -55°C.

Automotive-Grade Alternative:

BZT52H-C18,115 (Nexperia): 18 V, 375 mW, ±5% tolerance, 20 Ω impedance (lowest impedance option). AEC-Q101 automotive qualification. SOD-123F package variant. Operating temperature -65°C to 150°C. ROHS3 compliant. Recommended for automotive and high-reliability applications.

Not Recommended:

BZT52C18-TP (Micro Commercial Co): 200 mW power rating is significantly below the original 500 mW specification and may not be suitable for circuits designed for the higher power dissipation capability.
MMSZ4705-HE3-08 (Vishay): Product status is Obsolete. While specifications match, active availability is limited (2,387 units) compared to other alternatives.

Frequently Asked Questions (FAQ)

Q: Can MMSZ5248B-7-F be used as a direct drop-in replacement for MMSZ5248B-7?

A: Yes. MMSZ5248B-7-F is electrically and mechanically identical to MMSZ5248B-7. Both devices have 18 V nominal Zener voltage, 500 mW power rating, ±5% tolerance, 21 Ω impedance, and SOD-123 package. The primary difference is ROHS3 compliance status and active product availability. No circuit modifications are required.

Q: What is the difference between SOD-123 and SOD-123F packages?

A: SOD-123F is a variant of the SOD-123 package with enhanced mechanical robustness. Both packages are surface mount compatible with identical pin configurations and footprints. SOD-123F is used in the BZT52H-C18,115 part. Existing PCB designs for SOD-123 can accommodate SOD-123F devices without layout changes.

Q: Why do some substitute parts have lower power ratings (410 mW or 200 mW) than the original 500 mW?

A: Lower power ratings indicate reduced maximum power dissipation capability. Parts with 410 mW ratings (BZT52B18 and BZT52C18 series) are suitable for circuits where the Zener diode dissipates less than 410 mW. The 200 mW BZT52C18-TP is appropriate only for low-power applications. Circuit analysis is required to confirm that the substitute part's power rating is adequate for the intended application.

Q: What does impedance (Zzt) mean, and why does it vary among substitutes?

A: Impedance (Zzt) is the dynamic impedance of the Zener diode at the specified test current. Lower impedance values provide better voltage regulation and lower output impedance. The original MMSZ5248B-7 has 21 Ω impedance. Substitutes with higher impedance (45 Ω or 50 Ω) may exhibit slightly higher voltage ripple in regulation circuits. The BZT52H-C18,115 with 20 Ω impedance provides superior regulation performance.

Q: Are all substitute parts RoHS3 compliant?

A: All recommended substitute parts except the original MMSZ5248B-7 are ROHS3 compliant. MMSZ5248B-7 is RoHS non-compliant. If RoHS3 compliance is a design requirement, MMSZ5248B-7-F, MMSZ18T1G, MMSZ18ET1G, BZT52 series, and BZT52H-C18,115 are all suitable options.

Q: Can I use MMSZ18T1G or MMSZ18ET1G as replacements if the operating temperature range is -65°C to 150°C?

A: MMSZ18T1G and MMSZ18ET1G have an operating temperature range of -55°C to 150°C, which is narrower at the low end. These parts are suitable only if the circuit operates above -55°C. For applications requiring operation down to -65°C, use MMSZ5248B-7-F, BZT52B18 series, BZT52C18-TP, or BZT52H-C18,115.

Q: What is the difference between BZT52B18 and BZT52C18 series?

A: The primary difference is voltage tolerance. BZT52B18 series has ±2% tolerance (tighter), while BZT52C18 series has ±5% or ±6% tolerance (looser). Both series have 18 V nominal Zener voltage and SOD-123 package. BZT52B18 is preferred for applications requiring tighter voltage regulation. BZT52C18 is suitable for general-purpose applications with relaxed tolerance requirements.

Q: Is BZT52H-C18,115 suitable for non-automotive applications?

A: Yes. BZT52H-C18,115 is AEC-Q101 automotive qualified, but this certification does not restrict its use to automotive applications. The part is suitable for any application requiring 18 V, 375 mW Zener diode functionality. The automotive qualification indicates enhanced reliability and quality assurance, making it appropriate for high-reliability applications across all industries.

Q: What packaging options are available for substitute parts?

A: Substitute parts are available in Tape & Reel (TR) and Cut Tape (CT) & Digi-Reel® packaging. Tape & Reel packaging is standard for automated assembly processes. Cut Tape & Digi-Reel® packaging is suitable for lower-volume manual assembly or prototyping. All parts maintain identical electrical specifications regardless of packaging format.

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