SMAJ18A-13 Equivalent & Substitute Parts

Part Overview

The SMAJ18A-13 is a transient voltage suppressor (TVS) diode manufactured by Diodes Incorporated in the DO-214AC (SMA) surface mount package. This unidirectional Zener diode is designed for general-purpose transient voltage suppression with an 18V reverse standoff voltage and 29.2V maximum clamping voltage at peak pulse current of 13.7A. The part is currently obsolete, necessitating identification of active equivalent and substitute components that maintain electrical and mechanical compatibility for new designs or production continuity.

Key Parameters

Parameter	Value
Voltage - Reverse Standoff (Typ)	18V
Voltage - Breakdown (Min)	20V
Voltage - Clamping (Max) @ Ipp	29.2V
Current - Peak Pulse (10/1000µs)	13.7A
Power - Peak Pulse	400W
Operating Temperature Range	-55°C ~ 150°C (TJ)
Package / Case	DO-214AC, SMA
Mounting Type	Surface Mount
Type	Zener
Unidirectional Channels	1

Substitute Part Grouping Explanation

Substitution of the SMAJ18A-13 is determined by the following electrical and mechanical criteria:

Primary Substitution Criteria:

Voltage - Reverse Standoff: 18V (required match)
Voltage - Breakdown (Min): 20V (required match)
Voltage - Clamping (Max) @ Ipp: 29.2V (required match for standard performance)
Current - Peak Pulse: minimum 13.7A at 10/1000µs pulse width
Power - Peak Pulse: minimum 400W
Package / Case: DO-214AC (SMA) or SOD-123W (for space-constrained applications)
Mounting Type: Surface Mount
Type: Zener, Unidirectional (1 channel)

Secondary Considerations:

Product Status: Active preferred (obsolete parts subject to availability constraints)
RoHS Compliance: ROHS3 Compliant preferred for regulatory alignment
Operating Temperature Range: -55°C minimum to 150°C minimum required
Moisture Sensitivity Level: 1 (Unlimited) preferred

Parts meeting all primary criteria are classified as direct electrical equivalents. Parts with higher clamping voltage or peak pulse current ratings are classified as performance-enhanced substitutes suitable for applications requiring additional margin.

Parameter Comparison

Part Number	Manufacturer	Vwm (Typ)	Vbr (Min)	Vc (Max) @ Ipp	Ipp (10/1000µs)	Power (Peak)	Package	Status	RoHS
SMAJ18A-13	Diodes Incorporated	18V	20V	29.2V	13.7A	400W	DO-214AC (SMA)	Obsolete	Non-compliant
SMAJ18A-13-F	Diodes Incorporated	18V	20V	29.2V	13.7A	400W	DO-214AC (SMA)	Active	ROHS3
TV04A180J-G	Comchip Technology	18V	20V	29.2V	13.7A	400W	DO-214AC (SMA)	Active	ROHS3
PTVS18VS1UR,115	Nexperia USA Inc.	18V	20V	29.2V	13.7A	400W	SOD-123W	Active	ROHS3
SM4T21AY	STMicroelectronics	18V	20V	39.3V	59A (8/20µs)	400W	DO-214AC (SMA)	Active	ROHS3
SMA6J18A-TP	Micro Commercial Co	18V	20V	29.2V	20.5A	600W	DO-214AC (SMA)	Active	ROHS3
SMA6J18A-TR	STMicroelectronics	18V	20V	33.2V	102A (8/20µs)	600W	DO-214AC (SMA)	Active	ROHS3
SMAJ18A	MDD	18V	20V	29.2V	13.7A	400W	DO-214AC (SMA)	Active	ROHS3
SMAJ18A-TP	Micro Commercial Co	18V	20V	29.2V	13.7A	400W	DO-214AC (SMA)	Active	ROHS3
SMAJ18A-TR	STMicroelectronics	18V	20V	39.3V	59A (8/20µs)	400W	DO-214AC (SMA)	Active	ROHS3

Engineering Selection Recommendations

Direct Electrical Equivalents (Identical Electrical Performance):

SMAJ18A-13-F (Diodes Incorporated), TV04A180J-G (Comchip Technology), SMAJ18A (MDD), and SMAJ18A-TP (Micro Commercial Co) provide identical electrical specifications to the SMAJ18A-13. All are active products with ROHS3 compliance. SMAJ18A-13-F is the direct successor from the original manufacturer. TV04A180J-G and SMAJ18A-TP offer equivalent performance from alternative manufacturers with established supply availability.

Package Variant (Electrical Equivalent, Different Package):

PTVS18VS1UR,115 (Nexperia USA Inc.) matches all electrical parameters but uses SOD-123W package instead of DO-214AC (SMA). This variant is suitable for space-constrained designs and includes AEC-Q101 automotive qualification. Selection requires PCB layout compatibility with SOD-123W footprint.

Performance-Enhanced Substitutes (Higher Current/Power Ratings):

SMA6J18A-TP (Micro Commercial Co) and SMA6J18A-TR (STMicroelectronics) maintain the 18V/20V voltage specifications with higher peak pulse current (20.5A and 102A respectively) and increased power dissipation (600W). These parts provide additional transient suppression margin and are suitable for applications with higher surge current requirements.

SM4T21AY (STMicroelectronics) and SMAJ18A-TR (STMicroelectronics) offer elevated clamping voltage (39.3V) with significantly higher peak pulse current (59A at 8/20µs). These are suitable for applications requiring enhanced transient protection with higher energy absorption capacity.

All recommended substitutes are active products with ROHS3 compliance and unlimited moisture sensitivity rating (MSL 1).

Frequently Asked Questions (FAQ)

Q: Can SMAJ18A-13-F be used as a direct replacement for SMAJ18A-13?

A: Yes. SMAJ18A-13-F is the active production equivalent from Diodes Incorporated with identical electrical specifications (18V standoff, 20V breakdown, 29.2V clamping, 13.7A peak pulse current, 400W power). The primary difference is product status (active vs. obsolete) and RoHS compliance (ROHS3 vs. non-compliant). Footprint and pinout are identical.

Q: What is the difference between DO-214AC (SMA) and SOD-123W packages?

A: Both are surface mount packages for TVS diodes with identical electrical performance. DO-214AC (SMA) is the larger package; SOD-123W is a smaller variant. PTVS18VS1UR,115 uses SOD-123W and is suitable for space-constrained PCB layouts. Package selection depends on available board space and design requirements.

Q: Can I use SMA6J18A-TP or SMA6J18A-TR as substitutes?

A: Yes, with design considerations. Both maintain the 18V reverse standoff voltage required for the application. SMA6J18A-TP provides higher peak pulse current (20.5A vs. 13.7A) and power (600W vs. 400W) with identical clamping voltage (29.2V). SMA6J18A-TR offers even higher current (102A) and elevated clamping voltage (33.2V). These are suitable for applications requiring additional transient suppression margin or higher surge current handling.

Q: What does AEC-Q101 qualification mean for PTVS18VS1UR,115?

A: AEC-Q101 is an automotive qualification standard. PTVS18VS1UR,115 meets automotive-grade reliability requirements and is suitable for automotive and industrial applications requiring enhanced quality assurance. This certification is not required for general-purpose applications but provides additional confidence in product reliability.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All recommended substitute parts are ROHS3 compliant. The original SMAJ18A-13 is RoHS non-compliant. Substitution with any recommended part ensures regulatory compliance with RoHS3 requirements.

Q: What is the difference between 10/1000µs and 8/20µs pulse width specifications?

A: These represent different test pulse waveforms for measuring peak pulse current. 10/1000µs is a longer, slower pulse; 8/20µs is a faster pulse. Parts specified with 8/20µs (SM4T21AY, SMAJ18A-TR, SMA6J18A-TR) demonstrate higher peak current capability under faster transient conditions. Both specifications are valid for TVS diode characterization; selection depends on the actual transient waveform in the application.

Q: Can I substitute a part with higher clamping voltage?

A: Yes, with circuit analysis. Higher clamping voltage (39.3V vs. 29.2V) means the protected circuit experiences higher voltage during transient events. This is acceptable if the protected components tolerate the higher voltage. Lower clamping voltage provides tighter voltage regulation but may limit current handling capacity. Application requirements determine the appropriate clamping voltage.

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