1N4746AW-TP Zener Diode Equivalent & Substitute Parts

Part Overview

The 1N4746AW-TP is an 18 V, 1 W surface mount zener diode manufactured by Micro Commercial Co in SOD-123 package. This component is classified as obsolete, necessitating identification of active equivalent and substitute parts for ongoing design requirements and production continuity. The 18 V nominal zener voltage with ±5% tolerance and 1 W maximum power dissipation define the primary electrical specifications for substitution evaluation.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	18	V
Tolerance	±5%	—
Power - Max	1	W
Impedance (Max)	20	Ohms
Current - Reverse Leakage @ Vr	5	µA @ 13.7 V
Voltage - Forward (Max) @ If	1.2	V @ 200 mA
Operating Temperature Range	-55 to 150	°C
Mounting Type	Surface Mount	—
Package / Case	SOD-123	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the 1N4746AW-TP is determined by the following critical parameters:

Primary Electrical Criteria:

Zener voltage: 18 V nominal
Tolerance: ±5% or tighter
Power dissipation capability: minimum 1 W for direct replacement; lower power ratings (500 mW, 300 mW, 200 mW) constitute functional substitutes for reduced power applications
Operating temperature range: -55°C to 150°C minimum

Package and Mounting Criteria:

Surface mount technology required
SOD-123 package preferred for direct mechanical compatibility; SOD-123F, SOD-323, and SOD-523 packages represent alternative form factors with different thermal and spatial characteristics

Compliance Criteria:

ROHS3 compliance required
Moisture sensitivity level 1 (unlimited) preferred

Substitute parts are grouped into two categories: Direct Substitutes (equivalent power rating and package) and Functional Substitutes (reduced power rating or alternative package, suitable for applications with lower power requirements).

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance	Power (W/mW)	Package	Zzt (Ohms)	Temp Range (°C)	Status
1N4746AW-TP	Micro Commercial Co	18	±5%	1 W	SOD-123	20	-55 to 150	Obsolete
DFLZ18-TP	Micro Commercial Co	18	±6%	1 W	SOD-123F	15	-55 to 150	Active
MMSZ18T1G	onsemi	18	±5%	500 mW	SOD-123	45	-55 to 150	Active
MMSZ4705T1G	onsemi	18	±5%	500 mW	SOD-123	45	-55 to 150	Active
MMSZ5248B-7-F	Diodes Incorporated	18	±5%	500 mW	SOD-123	21	-65 to 150	Active
MMSZ5248B-E3-08	Vishay General Semiconductor	18	±5%	500 mW	SOD-123	21	-55 to 150	Active
MMSZ5248CT1G	onsemi	18	±2%	500 mW	SOD-123	21	-55 to 150	Active
SZMMSZ18ET1G	onsemi	18	±5%	500 mW	SOD-123	45	-55 to 150	Active
SZMMSZ18T1G	onsemi	18	±5%	500 mW	SOD-123	45	-55 to 150	Active
BZT52C18T-7	Diodes Incorporated	18	±6%	300 mW	SOD-523	45	-65 to 150	Active
DDZ9705S-7	Diodes Incorporated	18	±5%	200 mW	SOD-323	—	-65 to 150	Active

Engineering Selection Recommendations

Direct Equivalent (1 W Power Rating, SOD-123 Package):

The DFLZ18-TP from Micro Commercial Co provides the closest direct equivalent to the 1N4746AW-TP. Both components share the same manufacturer, 1 W power rating, and SOD-123 package family. The DFLZ18-TP is active and ROHS3 compliant. The tolerance specification of ±6% on the DFLZ18-TP is marginally wider than the original ±5%, and impedance is improved at 15 Ohms versus 20 Ohms. This part is suitable for direct replacement in existing designs without modification.

Functional Substitutes (500 mW Power Rating, SOD-123 Package):

Multiple active alternatives provide 500 mW power dissipation in SOD-123 package:

MMSZ5248B-E3-08 (Vishay General Semiconductor): ±5% tolerance, 21 Ohms impedance, -55°C to 150°C operating range. ROHS3 compliant.
MMSZ5248B-7-F (Diodes Incorporated): ±5% tolerance, 21 Ohms impedance, extended temperature range -65°C to 150°C. ROHS3 compliant.
MMSZ5248CT1G (onsemi): ±2% tolerance (tighter than original), 21 Ohms impedance, -55°C to 150°C operating range. ROHS3 compliant. Offers superior voltage tolerance.
MMSZ18T1G (onsemi): ±5% tolerance, 45 Ohms impedance, -55°C to 150°C operating range. ROHS3 compliant.
MMSZ4705T1G (onsemi): ±5% tolerance, -55°C to 150°C operating range. ROHS3 compliant.
SZMMSZ18T1G (onsemi): ±5% tolerance, automotive grade with AEC-Q101 qualification, 45 Ohms impedance, -55°C to 150°C operating range. ROHS3 compliant. Suitable for automotive applications.
SZMMSZ18ET1G (onsemi): ±5% tolerance, automotive grade with AEC-Q101 qualification, 45 Ohms impedance, -55°C to 150°C operating range. ROHS3 compliant.

These 500 mW alternatives are suitable for applications where the original 1 W power dissipation is not required. Thermal design and circuit analysis must confirm adequate power margin.

Alternative Packages (Reduced Power Ratings):

BZT52C18T-7 (Diodes Incorporated): 300 mW, SOD-523 package, ±6% tolerance, -65°C to 150°C. ROHS3 compliant. Suitable for space-constrained applications with lower power requirements.
DDZ9705S-7 (Diodes Incorporated): 200 mW, SOD-323 package, ±5% tolerance, -65°C to 150°C. ROHS3 compliant. Smallest footprint option for minimal power applications.

All substitute parts listed are ROHS3 compliant and maintain the 18 V nominal zener voltage specification.

Frequently Asked Questions (FAQ)

Q: Can the DFLZ18-TP directly replace the 1N4746AW-TP without circuit modification?

A: Yes. The DFLZ18-TP maintains equivalent electrical performance (18 V zener voltage, 1 W power rating) and operates across the same temperature range (-55°C to 150°C). The SOD-123F package is mechanically compatible with SOD-123 footprints. The ±6% tolerance is acceptable for most applications requiring ±5% or wider tolerance specifications.

Q: Why are 500 mW alternatives listed if the original part is rated 1 W?

A: The 500 mW alternatives are functional substitutes for applications where the full 1 W dissipation capability is not required. Circuit analysis must confirm that peak power dissipation does not exceed 500 mW. These parts offer active status and multiple manufacturer options, improving supply chain flexibility.

Q: What is the difference between SOD-123, SOD-123F, SOD-323, and SOD-523 packages?

A: These are distinct surface mount package outlines with different physical dimensions and thermal characteristics. SOD-123 and SOD-123F are similar in size; SOD-323 is smaller; SOD-523 is the smallest. Package selection depends on PCB layout constraints and thermal requirements. Footprint compatibility must be verified before substitution.

Q: Are automotive-grade alternatives (SZMMSZ18T1G, SZMMSZ18ET1G) suitable for non-automotive applications?

A: Yes. Automotive-grade components with AEC-Q101 qualification meet or exceed standard industrial specifications. These parts are suitable for any application requiring the specified electrical parameters and operating temperature range.

Q: How does impedance (Zzt) affect substitution suitability?

A: Impedance affects voltage regulation characteristics under load changes. Lower impedance (15-21 Ohms) provides better voltage stability; higher impedance (45 Ohms) may result in greater voltage variation. For applications with stringent voltage regulation requirements, lower impedance alternatives (DFLZ18-TP, MMSZ5248 series) are preferred.

Q: Can I use a 200 mW or 300 mW part instead of the 1 W original?

A: Only if circuit analysis confirms that peak power dissipation does not exceed the substitute part's rating. These lower-power alternatives (DDZ9705S-7 at 200 mW, BZT52C18T-7 at 300 mW) are suitable for low-power applications but require thermal verification.

Q: What does ±2% tolerance mean compared to ±5%?

A: ±2% tolerance (MMSZ5248CT1G) provides tighter voltage regulation than ±5% or ±6%. The zener voltage will remain closer to the nominal 18 V across the specified operating range. This is beneficial for precision applications but not required for general-purpose voltage regulation.

Q: Are all listed substitutes ROHS3 compliant?

A: Yes. All substitute parts listed in this reference are ROHS3 compliant, meeting environmental and regulatory requirements equivalent to the original 1N4746AW-TP.

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