TPSMD18A Equivalent & Substitute Parts

Part Overview

The TPSMD18A is an 18V unidirectional Transient Voltage Suppressor (TVS) diode manufactured by Littelfuse Inc., designed for surface mount applications in the DO-214AB (SMC) package. This component provides transient overvoltage protection with a 29.2V clamping voltage and 102.7A peak pulse current capability at 3000W peak pulse power. The part is Active status and carries AEC-Q101 automotive qualification with ROHS3 compliance. Equivalent and substitute parts are identified to support procurement flexibility, supply chain continuity, and design standardization across compatible applications.

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)	102.7	A
Power - Peak Pulse	3000	W
Operating Temperature Range	-65 to 150	°C
Package / Case	DO-214AB, SMC	—
Mounting Type	Surface Mount	—
Type	Zener	—
Unidirectional Channels	1	—

Substitute Part Grouping Explanation

Substitute parts for the TPSMD18A are qualified based on strict electrical and mechanical parameter matching within the Transient Voltage Suppressor category. The substitution criteria are:

Voltage - Reverse Standoff (Typ): 18V
Voltage - Breakdown (Min): 20V
Voltage - Clamping (Max) @ Ipp: 29.2V
Current - Peak Pulse (10/1000µs): 102.7A ± 0.1A tolerance
Power - Peak Pulse: 3000W
Package / Case: DO-214AB, SMC
Mounting Type: Surface Mount
Type: Zener, Unidirectional (1 channel)
RoHS Status: ROHS3 Compliant

All identified substitutes meet these core electrical specifications and physical package requirements, ensuring functional equivalence in circuit protection applications.

Parameter Comparison

Parameter	TPSMD18A (Littelfuse)	SMDJ18A (Alpha & Omega)	SM30T21AY (STMicroelectronics)	SMDJE18AH (Eaton)
Voltage - Reverse Standoff (Typ)	18V	18V	18V	18V
Voltage - Breakdown (Min)	20V	20V	20V	20V
Voltage - Clamping (Max) @ Ipp	29.2V	29.2V	29.2V	29.2V
Current - Peak Pulse (10/1000µs)	102.7A	102.8A	102.7A	102.7A
Power - Peak Pulse	3000W	3000W	3000W	3000W
Operating Temperature Range	-65 to 150°C	-55 to 150°C	-55 to 175°C	-55 to 150°C
Package / Case	DO-214AB, SMC	DO-214AB, SMC	DO-214AB, SMC	DO-214AB, SMC
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Type	Zener	Zener	Zener	Zener
Unidirectional Channels	1	1	1	1
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Product Status	Active	Active	Active	Active
AEC-Q101 Qualification	Yes	Not specified	Yes	Yes
Moisture Sensitivity Level (MSL)	1 (Unlimited)	Not specified	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

All substitute parts listed maintain Active product status and ROHS3 compliance, ensuring regulatory alignment with the TPSMD18A. Selection among these equivalents should be based on the following factors:

AEC-Q101 Automotive Qualification: The TPSMD18A, SM30T21AY, and SMDJE18AH carry AEC-Q101 automotive qualification. The SMDJ18A does not specify this qualification. For automotive applications requiring AEC-Q101 compliance, selection should be limited to TPSMD18A, SM30T21AY, or SMDJE18AH.

Operating Temperature Range: The TPSMD18A supports -65 to 150°C. The SM30T21AY extends to -55 to 175°C, providing wider high-temperature capability. The SMDJ18A and SMDJE18AH operate within -55 to 150°C. Temperature range selection depends on application thermal requirements.

Moisture Sensitivity Level (MSL): The TPSMD18A, SM30T21AY, and SMDJE18AH specify MSL 1 (Unlimited), indicating no moisture sensitivity constraints. The SMDJ18A does not specify MSL. For moisture-sensitive environments or long-term storage, parts with specified MSL 1 are preferred.

Peak Pulse Current: The SMDJ18A specifies 102.8A, a 0.1A variance from the TPSMD18A specification of 102.7A. This minor difference remains within typical component tolerance and does not affect functional equivalence.

Frequently Asked Questions (FAQ)

Q: Can SMDJ18A be used as a direct replacement for TPSMD18A in automotive applications?

A: The SMDJ18A meets all core electrical and mechanical parameters for functional equivalence. However, it does not specify AEC-Q101 automotive qualification. For applications requiring AEC-Q101 compliance, SM30T21AY or SMDJE18AH are recommended alternatives.

Q: What is the significance of the 0.1A difference in peak pulse current between TPSMD18A (102.7A) and SMDJ18A (102.8A)?

A: The 0.1A variance represents a 0.1% difference and falls within standard component manufacturing tolerance. Both parts deliver equivalent transient suppression performance in circuit protection applications.

Q: Are all substitute parts available in the same DO-214AB (SMC) package?

A: Yes. All substitute parts—SMDJ18A, SM30T21AY, and SMDJE18AH—are packaged in DO-214AB (SMC) with surface mount mounting type, ensuring mechanical and footprint compatibility with TPSMD18A.

Q: Which substitute part offers the widest operating temperature range?

A: The SM30T21AY supports -55 to 175°C, extending 25°C above the TPSMD18A maximum of 150°C. This makes SM30T21AY suitable for high-temperature applications exceeding TPSMD18A thermal limits.

Q: Do all substitute parts carry ROHS3 compliance?

A: Yes. TPSMD18A, SMDJ18A, SM30T21AY, and SMDJE18AH are all ROHS3 compliant, meeting environmental and regulatory requirements for electronic component manufacturing and use.

Q: What is the difference between REACH Status "REACH Unaffected" across all parts?

A: REACH Unaffected status indicates that these components do not contain substances of very high concern (SVHC) listed under the REACH regulation, ensuring compliance with European chemical safety requirements.

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