1SMB18AT3 Transient Voltage Suppressor Equivalent & Substitute Parts

Part Overview

The 1SMB18AT3 is a transient voltage suppressor (TVS) diode manufactured by onsemi, rated for 18V reverse standoff with 29.2V clamping voltage in SMB packaging. This component is classified as obsolete, making equivalent substitute parts necessary for new designs and ongoing production requirements. The part operates as a unidirectional Zener-type TVS diode for general-purpose transient voltage suppression applications.

Key Parameters

Parameter	Value
Manufacturer Part Number	1SMB18AT3
Manufacturer	onsemi
Category	Transient Voltage Suppressors (TVS)
Description	TVS DIODE 18V 29.2V SMB
Product Status	Obsolete
Type	Zener
Unidirectional Channels	1
Voltage - Reverse Standoff (Typ)	18V
Voltage - Clamping (Max) @ Ipp	29.2V
Power - Peak Pulse	600W
Mounting Type	Surface Mount
RoHS Status	RoHS non-compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution of the 1SMB18AT3 is determined by the following critical electrical and mechanical parameters:

Electrical Equivalence Criteria:

Voltage - Reverse Standoff (Typ): 18V
Voltage - Clamping (Max) @ Ipp: 29.2V
Power - Peak Pulse: 600W
Type: Zener, Unidirectional (1 channel)

Mechanical Compatibility Criteria:

Mounting Type: Surface Mount
Package / Case: SMB (DO-214AA) or equivalent footprint compatibility

Compliance Criteria:

RoHS Status: ROHS3 Compliant (preferred for new designs)
Moisture Sensitivity Level (MSL): 1 (Unlimited)
ECCN: EAR99
HTSUS: 8541.10.0080

All substitute parts listed maintain identical electrical specifications (18V standoff, 29.2V clamp, 600W peak pulse) and are available in active product status with current manufacturing support.

Parameter Comparison

Part Number	Manufacturer	Voltage - Reverse Standoff (Typ)	Voltage - Breakdown (Min)	Voltage - Clamping (Max) @ Ipp	Current - Peak Pulse (10/1000µs)	Power - Peak Pulse	Package / Case	Product Status	RoHS Status	Operating Temperature
1SMB18AT3	onsemi	18V	-	29.2V	-	600W	SMB	Obsolete	RoHS non-compliant	-
SMBJ18A	EVVO Semi	18V	20V	29.2V	20.6A	600W	DO-214AC, SMA	Active	ROHS3 Compliant	-65°C ~ 150°C (TJ)
SMBJ18A-TR	STMicroelectronics	18V	20V	29.2V	21.5A	600W	DO-214AA, SMB	Active	ROHS3 Compliant	-55°C ~ 150°C (TJ)
SMBJ18A-13-F	Diodes Incorporated	18V	20V	29.2V	20.5A	600W	DO-214AA, SMB	Active	ROHS3 Compliant	-55°C ~ 150°C (TJ)
SMBJ18A-TP	Micro Commercial Co	18V	20V	29.2V	20.5A	600W	DO-214AA, SMB	Active	ROHS3 Compliant	-55°C ~ 175°C (TJ)
PTVS18VP1UP,115	Nexperia USA Inc.	18V	20V	29.2V	20.5A	600W	SOD-128	Active	ROHS3 Compliant	-55°C ~ 150°C (TA)

Engineering Selection Recommendations

Direct SMB Package Substitutes (Preferred): SMBJ18A-TR (STMicroelectronics), SMBJ18A-13-F (Diodes Incorporated), and SMBJ18A-TP (Micro Commercial Co) are direct functional equivalents in SMB (DO-214AA) packaging. All three are active products with ROHS3 compliance, making them suitable for new designs and production environments requiring RoHS certification. SMBJ18A-TP offers the widest operating temperature range (-55°C ~ 175°C), beneficial for high-temperature applications.

Alternative Package Substitute: PTVS18VP1UP,115 (Nexperia USA Inc.) provides electrical equivalence but uses SOD-128 packaging instead of SMB. This part includes AEC-Q101 automotive qualification and is suitable for applications requiring automotive-grade components. Package change requires PCB layout modification.

SMA Package Alternative: SMBJ18A (EVVO Semi) maintains electrical specifications in SMA (DO-214AC) packaging. This represents a package variant requiring footprint verification before selection.

All substitute parts are ROHS3 compliant and carry MSL 1 (Unlimited) moisture sensitivity rating, matching the original part's environmental specifications.

Frequently Asked Questions (FAQ)

Q: Can I directly replace 1SMB18AT3 with SMBJ18A-TR? A: Yes. SMBJ18A-TR is a direct electrical equivalent with identical 18V standoff and 29.2V clamping specifications. Both use SMB (DO-214AA) packaging, requiring no PCB layout changes. SMBJ18A-TR is active product status with ROHS3 compliance.

Q: What is the difference between SMB and SMA packaging? A: SMB (DO-214AA) and SMA (DO-214AC) are different surface-mount diode packages with different footprints. SMB is larger than SMA. Substitution between these packages requires PCB layout verification and potential redesign.

Q: Why is PTVS18VP1UP,115 listed as a similar substitute rather than direct? A: PTVS18VP1UP,115 uses SOD-128 packaging instead of SMB, requiring PCB footprint changes. However, it maintains identical electrical parameters (18V standoff, 29.2V clamp, 600W peak pulse) and includes automotive qualification (AEC-Q101).

Q: Are all substitute parts RoHS compliant? A: Yes. All listed substitute parts carry ROHS3 compliance status. The original 1SMB18AT3 is RoHS non-compliant, making substitution necessary for applications requiring RoHS certification.

Q: What is the peak pulse current difference between substitutes? A: Peak pulse current varies slightly: SMBJ18A-TR at 21.5A, while SMBJ18A-13-F, SMBJ18A-TP, and PTVS18VP1UP,115 are rated at 20.5A. SMBJ18A (EVVO Semi) is rated at 20.6A. All values support the 600W peak pulse power specification.

Q: Which substitute has the widest operating temperature range? A: SMBJ18A-TP (Micro Commercial Co) operates from -55°C to 175°C, providing the widest temperature range among SMB package options.

Q: Can I use multiple substitute parts interchangeably in production? A: Yes, provided your design specifies SMB (DO-214AA) packaging. SMBJ18A-TR, SMBJ18A-13-F, and SMBJ18A-TP are all electrically and mechanically equivalent. Verify supplier availability and lead times for production planning.

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