3KASMC18HE3/9AT Transient Voltage Suppressor (TVS) Diode - Equivalent & Substitute Parts

Part Overview

The 3KASMC18HE3/9AT is a unidirectional Zener TVS diode manufactured by Vishay General Semiconductor - Diodes Division, designed for transient voltage suppression in surface mount applications. This component features an 18V reverse standoff voltage with 32.2V maximum clamping voltage and 93.2A peak pulse current capability in a DO-214AB (SMC) package. 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	32.2	V
Current - Peak Pulse (10/1000µs)	93.2	A
Power - Peak Pulse	3000	W
Operating Temperature Range	-65 to 185	°C (TJ)
Package / Case	DO-214AB, SMC	—
Mounting Type	Surface Mount	—
RoHS Status	ROHS3 Compliant	—
Grade	Automotive	—
Qualification	AEC-Q101	—

Substitute Part Grouping Explanation

Substitution of the 3KASMC18HE3/9AT is determined by strict equivalence across the following electrical and mechanical parameters:

Voltage - Reverse Standoff: 18V (nominal)
Voltage - Breakdown (Min): 20V
Voltage - Clamping (Max) @ Ipp: 32.2V or lower (acceptable for protection margin)
Current - Peak Pulse (10/1000µs): minimum 93.2A or higher
Power - Peak Pulse: minimum 3000W or higher
Package / Case: DO-214AB, SMC (surface mount)
Unidirectional Channels: 1
Type: Zener

Substitute parts are grouped into two categories based on electrical performance alignment:

Category A - Full Electrical Equivalents (32.2V Clamping): Parts maintaining the exact 32.2V clamping voltage specification with equivalent or superior current handling.

Category B - Functional Equivalents (29.2V Clamping): Parts with reduced clamping voltage (29.2V) but equivalent or superior current and power ratings, suitable for applications where lower clamping voltage provides enhanced protection margin.

Parameter Comparison

Part Number	Manufacturer	VWM (V)	VBR (Min, V)	VC (Max, V)	Ipp (A)	PPP (W)	Temp Range (°C)	Status
3KASMC18HE3/9AT	Vishay	18	20	32.2	93.2	3000	-65 to 185	Obsolete
SMLJ18E3/TR13	Microchip Technology	18	20	32.2	93.2	300	-55 to 150	Active
5.0SMDJ18A	Taiwan Semiconductor	18	20	29.2	172	5000	-55 to 175	Active
SMCJ18A	MDD	18	20	29.2	51.4	1500	-50 to 150	Active
SMCJ18A-TP	Micro Commercial Co	18	20	29.2	51.4	1500	-55 to 175	Active
SMCJ18AE3/TR13	Microchip Technology	18	20	29.2	51.4	1500	-65 to 150	Active
SMCJ18E3/TR13	Microchip Technology	18	20	32.2	46.6	1500	-65 to 150	Active
SMDJ18A	Alpha & Omega Semiconductor	18	20	29.2	102.8	3000	-55 to 150	Active
SMDJ18A-HR	Littelfuse Inc.	18	20	29.2	102.7	3000	-65 to 150	Active

Engineering Selection Recommendations

Primary Recommendation - Full Electrical Match:

SMCJ18E3/TR13 (Microchip Technology) maintains the 32.2V clamping voltage specification of the original part with active product status and AEC-Q101 automotive qualification path compatibility. This part is suitable for direct replacement in automotive-grade applications requiring exact voltage clamping performance.

Secondary Recommendation - Enhanced Performance:

5.0SMDJ18A (Taiwan Semiconductor Corporation) provides superior current handling (172A vs. 93.2A) and power dissipation (5000W vs. 3000W) with 29.2V clamping voltage. This part is recommended for applications where enhanced transient suppression margin is acceptable and beneficial.

Alternative for Standard Applications:

SMDJ18A-HR (Littelfuse Inc.) delivers 3000W peak pulse power with 102.7A peak current and extended temperature range (-65°C to 150°C), matching the original part's power rating while providing active product status and established supply chain availability.

All recommended substitutes maintain DO-214AB (SMC) surface mount packaging, RoHS3 compliance, and unidirectional Zener topology. Selection should account for application-specific temperature requirements and clamping voltage tolerance.

Frequently Asked Questions (FAQ)

Q: Can SMCJ18A (1500W) replace the 3KASMC18HE3/9AT (3000W)?

A: SMCJ18A is not suitable for direct replacement in applications requiring 3000W peak pulse power dissipation. The part's 1500W rating represents a 50% reduction in transient energy handling capacity. Use only in applications with confirmed lower transient energy requirements.

Q: What is the difference between 32.2V and 29.2V clamping voltage specifications?

A: The 3KASMC18HE3/9AT clamps at 32.2V maximum, while Category B substitutes (SMCJ18A, SMDJ18A, SMDJ18A-HR) clamp at 29.2V. The lower clamping voltage provides tighter voltage regulation and enhanced protection margin. Both specifications meet the 18V reverse standoff and 20V minimum breakdown requirements. Selection depends on circuit tolerance for maximum clamping voltage.

Q: Are all substitute parts automotive-grade?

A: The original 3KASMC18HE3/9AT carries automotive grade designation with AEC-Q101 qualification. Substitute parts listed do not explicitly state automotive grade in provided specifications. Verify AEC-Q101 or equivalent automotive qualification with manufacturers for safety-critical automotive applications.

Q: What is the significance of packaging designations (TR, TP, E3)?

A: TR indicates Tape & Reel packaging for automated assembly. TP indicates Tape & Reel with specific supplier designation. E3 indicates RoHS3 compliance variant. All substitute parts maintain DO-214AB (SMC) case geometry compatible with original PCB footprints. Packaging designation affects supply format and handling but not electrical performance.

Q: Can I use SMLJ18E3/TR13 despite its lower power rating (300W)?

A: SMLJ18E3/TR13 is not suitable for applications requiring 3000W peak pulse power dissipation. The 300W rating represents a 90% reduction in transient energy handling. This part is suitable only for low-energy transient suppression applications with confirmed power requirements below 300W.

Q: What temperature range should I select for my application?

A: The original part operates -65°C to 185°C. Most active substitutes operate -55°C to 150°C or -65°C to 150°C. For applications requiring the full -65°C to 185°C range, SMCJ18E3/TR13 and SMDJ18A-HR support -65°C minimum. Verify application temperature requirements before selection.

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