SMF18A-M3-08 Equivalent & Substitute Parts

Part Overview

The SMF18A-M3-08 is an 18V Transient Voltage Suppressor (TVS) diode manufactured by Vishay General Semiconductor - Diodes Division. This unidirectional Zener-type TVS diode is designed for general-purpose transient voltage suppression applications, featuring a 29.2V maximum clamping voltage and 6.8A peak pulse current capability. The device is packaged in DO-219AB (SMF) surface mount format and is ROHS3 compliant with AEC-Q101 automotive qualification available in select variants. Substitute parts are identified when equivalent electrical performance and mechanical compatibility are required due to inventory constraints, manufacturing discontinuation, or design flexibility needs.

Key Parameters

Parameter	Value	Unit
Voltage - Reverse Standoff (Typ)	18	V
Voltage - Breakdown (Min)	20	V
Voltage - Clamping (Max) @ Ipp	29.2	V
Current - Peak Pulse (10/1000µs)	6.8	A
Power - Peak Pulse	200	W
Capacitance @ 1MHz	320	pF
Operating Temperature Range	-65 to 175	°C
Package / Case	DO-219AB (SMF)	—
Mounting Type	Surface Mount	—

Substitute Part Grouping Explanation

Substitute parts for the SMF18A-M3-08 are classified into two categories based on electrical and mechanical compatibility:

Category 1: Direct Electrical & Package Equivalents Parts that maintain identical electrical specifications (18V standoff, 29.2V clamping, 6.8A peak pulse) and use the same DO-219AB package footprint. These substitutes differ only in manufacturer, packaging configuration (Tape & Reel variant), or automotive qualification level.

Category 2: Electrical Equivalents with Package Variation Parts that maintain identical electrical specifications but use alternative surface mount packages (SOD-123F/SOD-123FL). These require PCB layout modification but provide functional equivalence.

Key Parameters Determining Substitution:

Voltage - Reverse Standoff: 18V (required)
Voltage - Clamping (Max) @ Ipp: 29.2V (required)
Current - Peak Pulse: 6.8A (required)
Power - Peak Pulse: 200W (required)
Unidirectional Channels: 1 (required)
Type: Zener (required)
RoHS Status: ROHS3 Compliant (required)

Parameter Comparison

Parameter	SMF18A-M3-08	SMF18A-HM3-08	PTVS64VS1UTR,115	SMF18A-TP
Manufacturer	Vishay	Vishay	Nexperia	Micro Commercial Co
Voltage - Reverse Standoff (Typ)	18V	18V	64V	18V
Voltage - Breakdown (Min)	20V	20V	71.1V	20V
Voltage - Clamping (Max) @ Ipp	29.2V	29.2V	103V	29.2V
Current - Peak Pulse (10/1000µs)	6.8A	6.8A	3.9A	6.8A
Power - Peak Pulse	200W	200W	400W	200W
Operating Temperature Range	-65 to 175°C (TJ)	-65 to 175°C (TJ)	-55 to 185°C (TA)	-65 to 175°C (TA)
Package / Case	DO-219AB (SMF)	DO-219AB (SMF)	SOD-123W	SOD-123F
Automotive Grade	—	AEC-Q101	AEC-Q101	—
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

SMF18A-HM3-08 (Vishay): Direct substitute with identical electrical specifications and DO-219AB package compatibility. This variant includes AEC-Q101 automotive qualification, making it suitable for automotive applications requiring formal qualification documentation. Inventory availability is higher (27,339 pcs) compared to the primary part.

SMF18A-TP (Micro Commercial Co): Functionally equivalent with identical electrical performance but uses SOD-123F package instead of DO-219AB. Selection requires PCB redesign to accommodate the different footprint. No automotive qualification is specified for this variant. Suitable for general-purpose applications where package footprint modification is acceptable.

PTVS64VS1UTR,115 (Nexperia): Not recommended as a direct substitute. While this part carries AEC-Q101 automotive qualification and higher power rating (400W), it operates at 64V standoff voltage with 103V clamping voltage—significantly different from the 18V/29.2V specifications of the primary part. This device is designed for higher voltage protection circuits and is not electrically compatible with 18V suppression requirements.

Frequently Asked Questions (FAQ)

Q: Can SMF18A-HM3-08 be used as a direct replacement for SMF18A-M3-08? A: Yes. Both parts share identical electrical specifications (18V standoff, 29.2V clamping, 6.8A peak pulse) and use the same DO-219AB package footprint. The primary difference is that SMF18A-HM3-08 includes AEC-Q101 automotive qualification. No PCB modifications are required.

Q: What is the difference between SMF18A-M3-08 and SMF18A-TP? A: Both parts have identical electrical performance. The difference is packaging: SMF18A-M3-08 uses DO-219AB (SMF) while SMF18A-TP uses SOD-123F. These packages have different footprints and pin configurations, requiring PCB layout changes for substitution.

Q: Is PTVS64VS1UTR,115 compatible with SMF18A-M3-08? A: No. Although both are TVS diodes with AEC-Q101 qualification, PTVS64VS1UTR,115 is rated for 64V standoff voltage with 103V clamping, making it unsuitable for 18V protection circuits. Using this part would result in inadequate transient suppression for the intended application.

Q: What does AEC-Q101 qualification mean? A: AEC-Q101 is an automotive industry qualification standard for discrete semiconductors. It certifies that the component meets reliability and quality requirements for automotive applications. SMF18A-HM3-08 carries this qualification; the primary SMF18A-M3-08 does not.

Q: Can I use SMF18A-TP if I modify my PCB layout? A: Yes, provided your design allows for package footprint changes. SMF18A-TP delivers identical electrical performance and is ROHS3 compliant. Verify that the SOD-123F package dimensions and pin spacing are compatible with your PCB design constraints.

Q: What is the moisture sensitivity level (MSL) and why does it matter? A: All listed parts have MSL 1 (Unlimited), meaning they have unlimited shelf life and require no special moisture control during storage or handling. This simplifies inventory management and reduces component preparation requirements.

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