MM3Z18VST1 Equivalent & Substitute Parts

Part Overview

The MM3Z18VST1 is a Zener diode rated at 18 V nominal voltage with 200 mW maximum power dissipation in a surface mount SOD-323 package. Manufactured by onsemi, this component is classified as obsolete product status. Due to its obsolete designation, locating direct inventory of the MM3Z18VST1 becomes challenging for new designs and production requirements. Equivalent and substitute parts with active product status provide viable alternatives that maintain electrical and mechanical compatibility within specified parameter tolerances.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	18	V
Tolerance	±2%	-
Power - Max	200	mW
Impedance (Max)	45	Ohms
Current - Reverse Leakage @ Vr	50	nA @ 12.6 V
Voltage - Forward (Vf) (Max) @ If	900	mV @ 10 mA
Operating Temperature Range	-65 to 150	°C
Mounting Type	Surface Mount	-
Package / Case	SC-76, SOD-323	-

Substitute Part Grouping Explanation

Substitution of the MM3Z18VST1 is determined by the following critical parameters that must remain constant or within acceptable ranges:

Fixed Parameters (Must Match Exactly):

Voltage - Zener (Nom): 18 V
Tolerance: ±2%
Mounting Type: Surface Mount
Package / Case: SOD-323

Variable Parameters (Acceptable Ranges):

Power - Max: Substitute parts may exceed 200 mW (higher power ratings are backward compatible)
Impedance (Max): Substitute parts may vary within typical Zener diode specifications
Current - Reverse Leakage @ Vr: Substitute parts may vary within acceptable leakage specifications
Operating Temperature Range: Substitute parts must cover the required operating window

Substitute parts are grouped into two categories:

Direct Manufacturer Equivalent: MM3Z18VST1G (onsemi) provides identical electrical specifications with increased power rating (300 mW) and active product status.

Cross-Manufacturer Alternatives: BZT52-B18S_R1_00001 (Panjit International Inc.) and PZU18B2A,115 (Nexperia USA Inc.) maintain the 18 V nominal voltage and ±2% tolerance with variations in power dissipation, impedance, and temperature range.

Parameter Comparison

Parameter	MM3Z18VST1	MM3Z18VST1G	BZT52-B18S_R1_00001	PZU18B2A,115
Manufacturer	onsemi	onsemi	Panjit International Inc.	Nexperia USA Inc.
Product Status	Obsolete	Active	Active	Active
Voltage - Zener (Nom)	18 V	18 V	18 V	18 V
Tolerance	±2%	±2%	±2%	±2%
Power - Max	200 mW	300 mW	200 mW	320 mW
Impedance (Max)	45 Ohms	45 Ohms	50 Ohms	20 Ohms
Current - Reverse Leakage @ Vr	50 nA @ 12.6 V	50 nA @ 12.6 V	100 nA @ 14 V	50 nA @ 13 V
Voltage - Forward (Vf) (Max) @ If	900 mV @ 10 mA	900 mV @ 10 mA	Not specified	1.1 V @ 100 mA
Operating Temperature Range	-65 to 150°C	-65 to 150°C	-55 to 150°C	-55 to 150°C
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Package / Case	SC-76, SOD-323	SC-76, SOD-323	SC-90, SOD-323F	SC-76, SOD-323
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

MM3Z18VST1G (onsemi) is the primary substitute for the MM3Z18VST1. This part maintains identical electrical specifications including voltage, tolerance, impedance, and forward voltage characteristics. The increased power rating of 300 mW provides additional thermal margin over the original 200 mW specification. Active product status ensures ongoing availability and supply chain continuity. ROHS3 compliance aligns with current environmental regulations. Operating temperature range remains -65 to 150°C, matching the original specification.

PZU18B2A,115 (Nexperia USA Inc.) serves as an alternative substitute with active product status and ROHS3 compliance. This part maintains the 18 V nominal voltage and ±2% tolerance. The 320 mW power rating exceeds the original specification. The impedance of 20 Ohms is lower than the original 45 Ohms, resulting in improved voltage regulation characteristics. Operating temperature range is -55 to 150°C, which covers the upper temperature requirement but does not extend to the lower -65°C limit of the original part.

BZT52-B18S_R1_00001 (Panjit International Inc.) provides an alternative with active product status and ROHS3 compliance. This part maintains the 18 V nominal voltage, ±2% tolerance, and 200 mW power rating matching the original specification. The impedance of 50 Ohms is slightly higher than the original 45 Ohms. Operating temperature range is -55 to 150°C. Package designation SC-90, SOD-323F differs from the original SC-76, SOD-323, requiring verification of physical footprint compatibility.

Frequently Asked Questions (FAQ)

Q: Can MM3Z18VST1G directly replace MM3Z18VST1 in existing designs?

A: Yes. MM3Z18VST1G maintains identical electrical specifications for voltage, tolerance, impedance, and forward voltage. The increased power rating of 300 mW provides additional thermal capability. Both parts use the same SC-76, SOD-323 package and surface mount configuration. No design modifications are required.

Q: What is the primary reason to substitute the MM3Z18VST1?

A: The MM3Z18VST1 carries obsolete product status, limiting availability for new production and long-term supply assurance. Substitute parts with active product status provide reliable sourcing for current and future applications.

Q: Are all substitute parts ROHS3 compliant?

A: MM3Z18VST1G, BZT52-B18S_R1_00001, and PZU18B2A,115 are all ROHS3 compliant. The original MM3Z18VST1 is RoHS non-compliant. Compliance with ROHS3 standards is required for applications subject to environmental regulations.

Q: Does the higher power rating of substitute parts affect circuit performance?

A: Higher power ratings (300 mW for MM3Z18VST1G and 320 mW for PZU18B2A,115) do not negatively affect circuit performance. These ratings indicate increased thermal capability and are backward compatible with designs requiring 200 mW or less.

Q: What is the significance of impedance differences among substitute parts?

A: Impedance affects voltage regulation characteristics at high frequencies. MM3Z18VST1 and MM3Z18VST1G both specify 45 Ohms impedance. PZU18B2A,115 specifies 20 Ohms (lower impedance, better high-frequency regulation), while BZT52-B18S_R1_00001 specifies 50 Ohms (slightly higher impedance). These differences are within typical Zener diode specifications and do not prevent substitution.

Q: Does the operating temperature range difference affect substitution?

A: MM3Z18VST1 operates from -65 to 150°C. BZT52-B18S_R1_00001 and PZU18B2A,115 operate from -55 to 150°C. If the application requires operation below -55°C, only MM3Z18VST1G maintains the full -65°C lower limit. For applications within -55 to 150°C, all substitutes are acceptable.

Q: Is the package difference between BZT52-B18S_R1_00001 (SC-90, SOD-323F) and the original (SC-76, SOD-323) significant?

A: Both packages are SOD-323 surface mount configurations. SC-90 and SC-76 designations indicate minor physical variations. Verify PCB footprint compatibility before selecting BZT52-B18S_R1_00001 to ensure mechanical fit on existing circuit boards.

Q: What is the reverse leakage current specification, and does it vary among substitutes?

A: Reverse leakage current is the small current flowing through the Zener diode in reverse bias. MM3Z18VST1 specifies 50 nA @ 12.6 V. BZT52-B18S_R1_00001 specifies 100 nA @ 14 V (higher leakage), while PZU18B2A,115 specifies 50 nA @ 13 V (comparable leakage). These variations are within acceptable ranges for Zener diode applications.

Q: Are all substitute parts available in the same packaging options?

A: MM3Z18VST1G is available in Cut Tape (CT) and Digi-Reel packaging. BZT52-B18S_R1_00001 and PZU18B2A,115 are available in Tape & Reel (TR) packaging. Verify packaging availability with your supplier based on production volume and handling requirements.

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