MMSZ18T1 Zener Diode 18V 500mW SOD-123 Equivalent & Substitute Parts

Part Overview

The MMSZ18T1 is a 18 V, 500 mW Zener diode manufactured by onsemi in SOD-123 surface mount packaging. This component is classified as obsolete product status. The MMSZ18T1 is no longer in active production, making identification of equivalent and substitute parts essential for ongoing design support, maintenance, and new production requirements. Equivalent parts maintain identical electrical and mechanical specifications, while substitute parts provide functional alternatives with minor parameter variations within acceptable engineering tolerances.

Key Parameters

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

Substitute Part Grouping Explanation

Substitution of the MMSZ18T1 is determined by the following critical parameters: Zener voltage (18 V nominal), tolerance (±5%), package type (SOD-123 surface mount), and operating temperature range (-55°C to 150°C). Parts are grouped into three categories based on substitution compatibility:

Direct Equivalents (Parametric Match): Parts with identical electrical specifications (18 V, 500 mW, ±5% tolerance, 45 Ohms impedance) and active product status. These parts are fully interchangeable with the obsolete MMSZ18T1.

Parametric Equivalents (onsemi Automotive Grade): onsemi parts with identical electrical specifications but automotive qualification (AEC-Q101). These provide enhanced reliability for automotive applications while maintaining full electrical compatibility.

Similar Parts (Reduced Power Rating): Vishay and Micro Commercial Co parts with matching 18 V Zener voltage and ±5% tolerance but reduced maximum power dissipation (410 mW or 200 mW). These parts maintain voltage regulation characteristics but operate at lower power levels. Micro Commercial Co BZT52C18-TP operates at 200 mW with ±6% tolerance and extended temperature range (-65°C to 150°C).

All substitute parts maintain SOD-123 packaging, surface mount mounting type, and operating temperature range compatibility with the original MMSZ18T1.

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance	Power (mW)	Zzt (Ohms)	Vr Leakage (nA)	Vf Max (mV)	Temp Range (°C)	Package	Status	RoHS
MMSZ18T1	onsemi	18	±5%	500	45	50 @ 12.6V	900 @ 10mA	-55 to 150	SOD-123	Obsolete	Non-compliant
MMSZ18T1G	onsemi	18	±5%	500	45	50 @ 12.6V	900 @ 10mA	-55 to 150	SOD-123	Active	ROHS3 Compliant
MMSZ18ET1G	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	—	-55 to 150	SOD-123	Active	ROHS3 Compliant
SZMMSZ18T1G	onsemi	18	±5%	500	45	50 @ 12.6V	—	-55 to 150	SOD-123	Active	ROHS3 Compliant
BZT52C18-E3-08	Vishay	18	±5%	410	45	100 @ 14V	—	-55 to 150	SOD-123	Active	ROHS3 Compliant
BZT52C18-E3-18	Vishay	18	±5%	410	45	100 @ 14V	—	-55 to 150	SOD-123	Active	ROHS3 Compliant
BZT52C18-G3-08	Vishay	18	±5%	410	45	100 @ 14V	—	-55 to 150	SOD-123	Active	ROHS3 Compliant
BZT52C18-G3-18	Vishay	18	±5%	410	45	100 @ 14V	—	-55 to 150	SOD-123	Active	ROHS3 Compliant
BZT52C18-HE3-08	Vishay	18	±5%	410	45	100 @ 14V	—	-55 to 150	SOD-123	Obsolete	ROHS3 Compliant
BZT52C18-TP	Micro Commercial Co	18	±6%	200	45	100 @ 12.6V	900 @ 10mA	-65 to 150	SOD-123	Active	ROHS3 Compliant

Engineering Selection Recommendations

Primary Recommendation - Direct Replacement: MMSZ18T1G is the preferred direct replacement for the obsolete MMSZ18T1. This part maintains identical electrical specifications (18 V, 500 mW, ±5% tolerance) and is in active production status with ROHS3 compliance. The MMSZ18T1G is available in Cut Tape and Digi-Reel packaging with substantial inventory (155,400 pcs).

Alternative - Tape & Reel Packaging: MMSZ18ET1G provides identical electrical performance to MMSZ18T1 with active product status and ROHS3 compliance. This part is supplied in Tape & Reel format and is suitable for high-volume automated assembly operations.

Automotive Applications: SZMMSZ18ET1G and SZMMSZ18T1G are onsemi automotive-grade equivalents with AEC-Q101 qualification. These parts maintain full electrical compatibility with the original MMSZ18T1 while providing enhanced reliability for automotive environments. Both are ROHS3 compliant and in active production.

Reduced Power Applications: Vishay BZT52C18 series parts (E3-08, E3-18, G3-08, G3-18) provide 18 V Zener regulation with 410 mW maximum power dissipation. These parts are suitable for applications where the full 500 mW capability is not required. All variants are ROHS3 compliant and in active production status.

Extended Temperature Range: Micro Commercial Co BZT52C18-TP operates across -65°C to 150°C temperature range with 200 mW power rating and ±6% tolerance. This part is appropriate for applications requiring extended low-temperature operation below -55°C.

Frequently Asked Questions (FAQ)

Q: Can MMSZ18T1G be used as a direct replacement for MMSZ18T1?

A: Yes. MMSZ18T1G is a direct equivalent with identical electrical specifications (18 V, 500 mW, ±5% tolerance, 45 Ohms impedance) and SOD-123 packaging. The primary difference is product status: MMSZ18T1G is in active production while MMSZ18T1 is obsolete. MMSZ18T1G is ROHS3 compliant, whereas MMSZ18T1 is RoHS non-compliant.

Q: What is the difference between MMSZ18T1G and MMSZ18ET1G?

A: Both parts are onsemi equivalents with identical electrical specifications. The primary difference is packaging format: MMSZ18T1G is supplied in Cut Tape and Digi-Reel format, while MMSZ18ET1G is supplied in Tape & Reel format. Selection depends on assembly equipment compatibility and production volume requirements.

Q: Can Vishay BZT52C18 series parts replace MMSZ18T1?

A: Vishay BZT52C18 series parts (BZT52C18-E3-08, BZT52C18-E3-18, BZT52C18-G3-08, BZT52C18-G3-18) maintain the 18 V Zener voltage and ±5% tolerance but have reduced maximum power dissipation (410 mW versus 500 mW). These parts are suitable for applications where power dissipation does not exceed 410 mW. All variants maintain SOD-123 packaging and -55°C to 150°C operating temperature range.

Q: What is the significance of the automotive-grade SZMMSZ18 parts?

A: SZMMSZ18ET1G and SZMMSZ18T1G are onsemi automotive-grade Zener diodes with AEC-Q101 qualification. These parts maintain identical electrical specifications to MMSZ18T1 but undergo additional qualification testing for automotive applications. Use these parts in automotive designs requiring enhanced reliability and compliance with automotive qualification standards.

Q: Why does BZT52C18-TP have different tolerance and temperature range?

A: BZT52C18-TP is manufactured by Micro Commercial Co and has ±6% tolerance (versus ±5%) and extended low-temperature operation (-65°C versus -55°C). The 200 mW power rating is significantly lower than MMSZ18T1. This part is suitable only for applications where power dissipation does not exceed 200 mW and where the ±6% tolerance is acceptable.

Q: Are all substitute parts ROHS3 compliant?

A: All active production substitute parts listed are ROHS3 compliant. The original MMSZ18T1 is RoHS non-compliant. If RoHS compliance is a design requirement, select from the active production equivalents: MMSZ18T1G, MMSZ18ET1G, SZMMSZ18ET1G, SZMMSZ18T1G, or Vishay BZT52C18 series variants.

Q: What packaging options are available for equivalent parts?

A: MMSZ18T1G is available in Cut Tape and Digi-Reel packaging. MMSZ18ET1G and SZMMSZ18T1G are supplied in Tape & Reel format. SZMMSZ18ET1G packaging format is not specified in available data. Select packaging based on assembly equipment requirements and production volume.

Q: Can I use BZT52C18-HE3-08 as a replacement?

A: BZT52C18-HE3-08 is an obsolete Vishay part with 410 mW power rating and automotive qualification (AEC-Q101). While electrically compatible for 18 V regulation, the reduced power rating (410 mW versus 500 mW) and obsolete status make it unsuitable for new designs. Active production alternatives are preferred.

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