MMSZ18ET1 Zener Diode Equivalent & Substitute Parts

Part Overview

The MMSZ18ET1 is an 18 V, 500 mW surface mount zener diode manufactured by onsemi in SOD-123 packaging. This part is classified as obsolete, which necessitates identification of equivalent and substitute components for ongoing design and procurement requirements. Active alternatives with identical or comparable electrical characteristics are available from the same manufacturer and qualified suppliers.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	18	V
Tolerance	±5%	-
Power - Max	500	mW
Impedance (Max)	45	Ohms
Current - Reverse Leakage @ Vr	50	nA @ 12.6 V
Voltage - Forward (Max) @ If	900	mV @ 10 mA
Operating Temperature Range	-55 to 150	°C
Mounting Type	Surface Mount	-
Package / Case	SOD-123	-

Substitute Part Grouping Explanation

Substitution of the MMSZ18ET1 is determined by the following critical parameters: nominal zener voltage (18 V), tolerance (±5%), maximum power dissipation (500 mW), impedance (45 Ohms maximum), reverse leakage current (50 nA @ 12.6 V), forward voltage (900 mV @ 10 mA), operating temperature range (-55°C to 150°C), and surface mount packaging format.

Substitute parts are grouped into two categories:

Direct Equivalents (Parametric Match): Parts with identical electrical specifications and SOD-123 packaging. These include MMSZ18ET1G, MMSZ18T1G, SZMMSZ18ET1G, and SZMMSZ18T1G, all manufactured by onsemi. These parts maintain all specified parameters and differ only in packaging format (Tape & Reel, Cut Tape, or Digi-Reel) and product status (Active vs. Obsolete).

Similar Alternatives (Parameter Variance): Parts with matching zener voltage (18 V) and tolerance (±5%) but differing in power rating, impedance, package type, or manufacturer. These include BZT52H-C18,115 (Nexperia, 375 mW, SOD-123F) and PDZ18B,115 (Nexperia, 400 mW, SOD-323). These alternatives are suitable when the application permits reduced power dissipation or alternative packaging.

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance	Power (mW)	Zzt (Ohms)	Ir @ Vr (nA)	Vf (mV)	Temp Range (°C)	Package	Status	RoHS
MMSZ18ET1	onsemi	18	±5%	500	45	50 @ 12.6V	900 @ 10mA	-55 to 150	SOD-123	Obsolete	Non-compliant
MMSZ18ET1G	onsemi	18	±5%	500	45	50 @ 12.6V	900 @ 10mA	-55 to 150	SOD-123	Active	ROHS3 Compliant
MMSZ18T1G	onsemi	18	±5%	500	45	50 @ 12.6V	900 @ 10mA	-55 to 150	SOD-123	Active	ROHS3 Compliant
SZMMSZ18ET1G	onsemi	18	±5%	500	45	50 @ 12.6V	900 @ 10mA	-55 to 150	SOD-123	Active	ROHS3 Compliant
SZMMSZ18T1G	onsemi	18	±5%	500	45	50 @ 12.6V	900 @ 10mA	-55 to 150	SOD-123	Active	ROHS3 Compliant
BZT52H-C18,115	Nexperia USA Inc.	18	±5%	375	20	50 @ 12.6V	900 @ 10mA	-65 to 150	SOD-123F	Active	ROHS3 Compliant
PDZ18B,115	Nexperia USA Inc.	18	±2%	400	20	50 @ 13V	1100 @ 100mA	-55 to 150	SOD-323	Active	ROHS3 Compliant

Engineering Selection Recommendations

Primary Recommendation: MMSZ18ET1G or MMSZ18T1G are direct parametric equivalents manufactured by onsemi with identical electrical specifications to the obsolete MMSZ18ET1. Both parts are active products with ROHS3 compliance. Selection between these two depends on packaging format requirements: MMSZ18ET1G is supplied in Tape & Reel format, while MMSZ18T1G is available in Cut Tape and Digi-Reel format. MMSZ18T1G offers significantly higher inventory availability (155,400 units).

Automotive-Grade Alternative: SZMMSZ18ET1G and SZMMSZ18T1G are automotive-qualified variants (AEC-Q101) with identical electrical parameters. These parts are suitable for applications requiring automotive-grade components and are ROHS3 compliant. SZMMSZ18T1G is supplied in Tape & Reel format.

Alternative Manufacturer Options: BZT52H-C18,115 (Nexperia) maintains the 18 V zener voltage and ±5% tolerance but operates at reduced power dissipation (375 mW vs. 500 mW) with lower impedance (20 Ohms vs. 45 Ohms). This part uses SOD-123F packaging and includes automotive qualification (AEC-Q101). PDZ18B,115 (Nexperia) provides 18 V zener voltage with tighter tolerance (±2%) and 400 mW power rating in SOD-323 packaging. Both Nexperia alternatives are ROHS3 compliant and active products.

Frequently Asked Questions (FAQ)

Q: Can MMSZ18ET1G be used as a direct replacement for MMSZ18ET1?

A: Yes. MMSZ18ET1G is a direct parametric equivalent with identical electrical specifications (18 V, ±5%, 500 mW, 45 Ohms impedance, -55°C to 150°C operating range) and SOD-123 packaging. The primary difference is product status: MMSZ18ET1G is active while MMSZ18ET1 is obsolete. MMSZ18ET1G is ROHS3 compliant.

Q: What is the difference between MMSZ18ET1G and MMSZ18T1G?

A: Both parts are parametrically identical with 18 V zener voltage, ±5% tolerance, 500 mW power rating, and SOD-123 packaging. The difference is packaging format: MMSZ18ET1G is supplied in Tape & Reel, while MMSZ18T1G is supplied in Cut Tape and Digi-Reel format. MMSZ18T1G has significantly higher inventory availability.

Q: When should automotive-grade variants (SZMMSZ18ET1G or SZMMSZ18T1G) be selected?

A: Automotive-grade variants should be selected when the application requires AEC-Q101 qualification or when the design specification mandates automotive-grade components. These parts maintain identical electrical parameters to the standard MMSZ18 series and are ROHS3 compliant.

Q: Can BZT52H-C18,115 replace MMSZ18ET1 in all applications?

A: BZT52H-C18,115 maintains the 18 V zener voltage and ±5% tolerance but operates at reduced maximum power dissipation (375 mW vs. 500 mW) and lower impedance (20 Ohms vs. 45 Ohms). This part is suitable for applications where the 375 mW power rating is sufficient. The package type differs (SOD-123F vs. SOD-123). BZT52H-C18,115 includes automotive qualification (AEC-Q101).

Q: What are the key differences between PDZ18B,115 and MMSZ18ET1?

A: PDZ18B,115 maintains the 18 V zener voltage but differs in multiple parameters: tolerance is ±2% (tighter than ±5%), maximum power is 400 mW (lower than 500 mW), impedance is 20 Ohms (lower than 45 Ohms), and packaging is SOD-323 (different from SOD-123). Forward voltage specification also differs. PDZ18B,115 is suitable for applications where the reduced power rating and tighter tolerance are acceptable.

Q: Are all substitute parts ROHS3 compliant?

A: All active substitute parts listed (MMSZ18ET1G, MMSZ18T1G, SZMMSZ18ET1G, SZMMSZ18T1G, BZT52H-C18,115, and PDZ18B,115) are ROHS3 compliant. The original MMSZ18ET1 is classified as RoHS non-compliant.

Q: What packaging formats are available for the MMSZ18 series?

A: onsemi supplies the MMSZ18 series in multiple packaging formats: Tape & Reel (MMSZ18ET1G), Cut Tape and Digi-Reel (MMSZ18T1G). Automotive variants are available in both formats. Alternative manufacturers offer SOD-123F (Nexperia BZT52H-C18,115) and SOD-323 (Nexperia PDZ18B,115) packages.

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