3KASMC18AHM3_A/H Transient Voltage Suppressor Diode - Equivalent & Substitute Parts

Part Overview

The 3KASMC18AHM3_A/H is an 18V Zener transient voltage suppressor (TVS) diode manufactured by Vishay General Semiconductor - Diodes Division, designed for surface mount applications in the DO-214AB (SMCJ) package. This unidirectional TVS diode provides transient overvoltage protection with a 29.2V maximum clamping voltage and 103A peak pulse current capability. The part is classified as obsolete, necessitating identification of active equivalent alternatives that maintain electrical and mechanical compatibility for new designs and production continuity.

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)	103	A
Power - Peak Pulse	3000	W
Operating Temperature Range	-65 to 185	°C (TJ)
Package / Case	DO-214AB, SMC	—
Type	Zener, Unidirectional	—
Grade	Automotive	—
Qualification	AEC-Q101	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution eligibility for the 3KASMC18AHM3_A/H is determined by the following critical parameters:

Mandatory Matching Parameters:

Voltage - Reverse Standoff (Typ): 18V
Voltage - Breakdown (Min): 20V
Voltage - Clamping (Max) @ Ipp: 29.2V
Package / Case: DO-214AB, SMC
Type: Zener, Unidirectional
Mounting Type: Surface Mount

Allowable Variation Parameters:

Current - Peak Pulse (10/1000µs): Equal to or greater than 103A
Power - Peak Pulse: Equal to or greater than 3000W
Operating Temperature Range: Must encompass or exceed -65°C to 185°C
Product Status: Active preferred for new designs; obsolete acceptable for legacy support only

Substitute parts are grouped into two categories: direct electrical equivalents with identical or superior electrical ratings, and functional alternatives that meet the core voltage protection requirements while accommodating different manufacturing sources and product statuses.

Parameter Comparison

Part Number	Manufacturer	Vwm (Typ) V	Vbr (Min) V	Vc (Max) @ Ipp V	Ipp A	Ppk W	Tj Range °C	Package	Status
3KASMC18AHM3_A/H	Vishay	18	20	29.2	103	3000	-65 to 185	DO-214AB	Obsolete
3KASMC18AHM3_B/H	Vishay	18	20	29.2	103	3000	-65 to 185	DO-214AB	Active
SMC30J18A	STMicroelectronics	18	20	29.2	103	3000	-55 to 175	DO-214AB	Active
5.0SMDJ18A	Taiwan Semiconductor Corporation	18	20	29.2	172	5000	-55 to 175	DO-214AB	Active
SMCJ18A	MDD	18	20	29.2	51.4	1500	-50 to 150	DO-214AB	Active
SMCJ18A-HR	Littelfuse Inc.	18	20	29.2	51.4	1500	-65 to 150	DO-214AB	Active
SMCJ18A-HRA	Littelfuse Inc.	18	20	29.2	51.4	1500	-65 to 150	DO-214AB	Active
SMCJ16A	EVVO Semi	16	17.8	26	57.7	600	-65 to 150	DO-214AC	Active

Engineering Selection Recommendations

Primary Substitutes (Direct Equivalents):

3KASMC18AHM3_B/H is the direct active equivalent from Vishay, maintaining identical electrical specifications and automotive-grade AEC-Q101 qualification. This part is the preferred replacement for the obsolete 3KASMC18AHM3_A/H variant.

SMC30J18A from STMicroelectronics provides equivalent voltage and current ratings with active product status. Operating temperature range is reduced to -55°C to 175°C, which is acceptable for most commercial and industrial applications but not suitable for extended automotive temperature ranges requiring -65°C operation.

5.0SMDJ18A from Taiwan Semiconductor Corporation exceeds the original specifications with 172A peak pulse current and 5000W power dissipation, providing enhanced transient protection margin. This part is suitable for applications requiring higher surge capacity while maintaining identical voltage characteristics.

Secondary Substitutes (Functional Alternatives):

SMCJ18A variants from MDD and Littelfuse Inc. (SMCJ18A-HR, SMCJ18A-HRA) maintain voltage specifications but provide reduced peak pulse current (51.4A) and power dissipation (1500W). These parts are suitable only for applications with lower transient energy requirements. Littelfuse variants extend the lower temperature limit to -65°C, matching the original specification.

Not Recommended:

SMCJ16A from EVVO Semi does not meet substitution criteria. The 16V reverse standoff voltage and 26V clamping voltage are below the required 18V and 29.2V specifications, resulting in inadequate overvoltage protection for circuits designed for the 3KASMC18AHM3_A/H.

Frequently Asked Questions (FAQ)

Q: Can I use 3KASMC18AHM3_B/H as a direct replacement for the obsolete 3KASMC18AHM3_A/H?

A: Yes. The 3KASMC18AHM3_B/H is electrically and mechanically identical to the original part, differing only in packaging format (Tape & Reel) and active product status. Both parts share the same base product number 3KASMC18 and maintain full automotive AEC-Q101 qualification.

Q: What is the difference between the 103A and 51.4A peak pulse current ratings?

A: Peak pulse current (Ipp) determines the maximum transient surge the diode can safely suppress. The original 3KASMC18AHM3_A/H handles 103A pulses with 3000W peak power dissipation. Alternatives with 51.4A ratings (MDD and Littelfuse variants) are suitable only for applications with lower transient energy. Selection depends on the actual surge current magnitude in your circuit.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All listed substitute parts maintain ROHS3 compliance, ensuring compatibility with environmental and regulatory requirements.

Q: Does operating temperature range affect substitution suitability?

A: Yes, for automotive and extended-temperature applications. The original part operates from -65°C to 185°C. STMicroelectronics SMC30J18A and Taiwan Semiconductor 5.0SMDJ18A are limited to -55°C to 175°C, which may be insufficient for automotive under-hood environments. Littelfuse SMCJ18A-HR and SMCJ18A-HRA extend the lower limit to -65°C, matching the original specification.

Q: Can I use the 5.0SMDJ18A with higher power rating in place of the original part?

A: Yes. The 5.0SMDJ18A exceeds all electrical specifications of the original part while maintaining identical voltage characteristics. Higher current and power ratings provide additional transient protection margin without compromising circuit function. This substitution is suitable for applications requiring enhanced surge capacity.

Q: What is the significance of the DO-214AB package designation?

A: DO-214AB is the industry-standard surface mount package for TVS diodes in the SMC form factor. All recommended substitutes use this package, ensuring mechanical and thermal compatibility with existing PCB layouts and assembly processes. SMCJ16A uses DO-214AC (SMA package), which is physically incompatible.

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