MM5Z18V Equivalent & Substitute Parts

Part Overview

The MM5Z18V is a Zener diode manufactured by onsemi, rated at 18 V nominal with 200 mW power dissipation in a SOD-523F surface mount package. This component is classified as obsolete, indicating that direct procurement from the original manufacturer may be limited or unavailable. Equivalent and substitute parts are necessary to maintain design continuity, ensure supply chain reliability, and support ongoing production requirements for applications utilizing this 18 V Zener diode specification.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	18	V
Tolerance	±6%	-
Power - Max	200	mW
Impedance (Max)	45	Ohms
Current - Reverse Leakage @ Vr	50	nA @ 12.6 V
Operating Temperature Range	-55 to 150	°C
Mounting Type	Surface Mount	-
Package / Case	SOD-523F	-

Substitute Part Grouping Explanation

Substitution of the MM5Z18V is determined by the following critical parameters: nominal Zener voltage (18 V), voltage tolerance, maximum power dissipation, impedance characteristics, reverse leakage current, operating temperature range, and surface mount package compatibility.

Substitute parts are grouped into two categories based on package type:

Category 1: SOD-523F Package (Direct Package Match) Parts maintaining the SOD-523F package footprint with 18 V nominal voltage. These substitutes may differ in power rating (200 mW to 300 mW), voltage tolerance (±2% to ±5%), and temperature range extensions.

Category 2: SOD-323 Package (Alternate Package) Parts with 18 V nominal voltage in SOD-323 or SOD-323F packages. These represent functional equivalents with different physical footprints and higher power ratings (300 mW to 550 mW).

All substitute parts maintain the following core specifications: 18 V nominal Zener voltage, 45 Ohms maximum impedance (except BZX84J-B18,115 at 20 Ohms), 50 nA reverse leakage current, and surface mount technology.

Parameter Comparison

Part Number	Manufacturer	Vz (Nom)	Tolerance	Power (Max)	Zzt (Max)	Package	Temp Range	Status
MM5Z18V	onsemi	18 V	±6%	200 mW	45 Ω	SOD-523F	-55 to 150°C	Obsolete
MM3Z18VT1G	onsemi	18 V	±6%	300 mW	45 Ω	SOD-323	-65 to 150°C	Active
BZX584C18_R1_00001	Panjit International Inc.	18 V	±5%	200 mW	45 Ω	SOD-523	-55 to 150°C	Active
BZX585-B18,115	Nexperia USA Inc.	18 V	±2%	300 mW	45 Ω	SOD-523	-65 to 150°C	Active
BZX585-C18,115	Nexperia USA Inc.	18 V	±5%	300 mW	45 Ω	SOD-523	-65 to 150°C	Active
BZX84J-B18,115	Nexperia USA Inc.	18 V	±2%	550 mW	20 Ω	SOD-323F	-65 to 150°C	Active

Engineering Selection Recommendations

For Direct Package Compatibility (SOD-523F):

BZX584C18_R1_00001 provides the closest functional match to MM5Z18V, maintaining 200 mW power rating and SOD-523 package footprint. This part is manufactured by Panjit International Inc. and carries active product status with RoHS3 compliance. Voltage tolerance is ±5%, which is tighter than the original ±6% specification.

BZX585-B18,115 and BZX585-C18,115 offer increased power dissipation (300 mW) within the same SOD-523 package footprint. Both parts are manufactured by Nexperia USA Inc. with active status and RoHS3 compliance. BZX585-B18,115 includes automotive-grade qualification (AEC-Q100) with ±2% voltage tolerance. BZX585-C18,115 maintains ±5% tolerance. Extended operating temperature range (-65 to 150°C) provides additional thermal margin.

For Alternate Package Compatibility (SOD-323/SOD-323F):

MM3Z18VT1G is an onsemi product maintaining the same manufacturer lineage as the original part. It provides 300 mW power rating in SOD-323 package with ±6% tolerance matching the original specification. Active product status and extended temperature range (-65 to 150°C) support long-term availability.

BZX84J-B18,115 offers the highest power dissipation (550 mW) with automotive-grade qualification (AEC-Q101) in SOD-323F package. This part is suitable for applications requiring enhanced thermal performance and automotive reliability standards. Impedance is reduced to 20 Ohms, providing improved voltage regulation characteristics.

Compliance and Certification:

All substitute parts maintain RoHS3 compliance, REACH unaffected status, and EAR99 export classification. Automotive-qualified options (BZX585-B18,115 with AEC-Q100 and BZX84J-B18,115 with AEC-Q101) are available for applications requiring automotive-grade components.

Frequently Asked Questions (FAQ)

Q: Can MM3Z18VT1G replace MM5Z18V directly on the PCB?

A: MM3Z18VT1G is functionally equivalent but uses a different package (SOD-323 versus SOD-523F). PCB layout modifications are required. The part maintains 18 V nominal voltage, ±6% tolerance, and extends the operating temperature range to -65°C. Power rating increases to 300 mW.

Q: What is the difference between BZX585-B18,115 and BZX585-C18,115?

A: Both parts are identical except for voltage tolerance. BZX585-B18,115 specifies ±2% tolerance and includes automotive-grade qualification (AEC-Q100). BZX585-C18,115 specifies ±5% tolerance without automotive qualification. Both provide 300 mW power in SOD-523 package.

Q: Is BZX584C18_R1_00001 a pin-for-pin equivalent?

A: BZX584C18_R1_00001 maintains the same SOD-523 package footprint as MM5Z18V and is functionally equivalent with matching 200 mW power rating. Voltage tolerance is ±5% versus the original ±6%. This part is manufactured by Panjit International Inc. and carries active product status.

Q: When should BZX84J-B18,115 be selected over other substitutes?

A: BZX84J-B18,115 is selected when applications require higher power dissipation (550 mW), improved voltage regulation (20 Ohms impedance), automotive-grade reliability (AEC-Q101), or extended thermal performance. The SOD-323F package is larger than SOD-523F, requiring PCB layout changes.

Q: Are all substitute parts RoHS compliant?

A: Yes. All substitute parts listed carry RoHS3 compliance status. All parts are REACH unaffected and classified as EAR99 for export purposes.

Q: What is the impact of voltage tolerance differences on circuit design?

A: The original MM5Z18V specifies ±6% tolerance, resulting in a voltage range of 16.92 V to 19.08 V. Substitute parts with tighter tolerances (±2% or ±5%) provide narrower voltage ranges, improving voltage regulation accuracy. Circuit designs must verify that the selected tolerance meets application requirements.

Q: Can substitute parts with higher power ratings be used in place of the 200 mW original?

A: Yes. Parts with higher power ratings (300 mW or 550 mW) are backward compatible in applications designed for 200 mW, provided the package footprint is compatible or PCB modifications are acceptable. Higher power ratings provide thermal margin and improved reliability under sustained current conditions.

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