SMAJ40 Equivalent & Substitute Parts

Part Overview

The SMAJ40 is a unidirectional transient voltage suppressor (TVS) diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection in surface-mount applications. This component features a 40V reverse standoff voltage with a 67.73V maximum clamping voltage and 6.2A peak pulse current capability in a DO-214AC (SMA) package. The SMAJ40 is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Key Parameters

Parameter	Value	Unit
Voltage - Reverse Standoff (Typ)	40	V
Voltage - Breakdown (Min)	42.08	V
Voltage - Clamping (Max) @ Ipp	67.73	V
Current - Peak Pulse (10/1000µs)	6.2	A
Power - Peak Pulse	400	W
Operating Temperature Range	-65 to 150	°C (TJ)
Package / Case	DO-214AC, SMA	—
Type	Zener	—
Unidirectional Channels	1	—
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the SMAJ40 is determined by strict adherence to the following electrical and mechanical parameters:

Primary Substitution Criteria:

Voltage - Reverse Standoff (Typ): 40V
Voltage - Breakdown (Min): 44.4V (allowable range for 40V standoff class)
Package / Case: DO-214AC, SMA (surface-mount compatibility)
Type: Zener (unidirectional TVS diode)
Unidirectional Channels: 1
RoHS Status: ROHS3 Compliant
Moisture Sensitivity Level (MSL): 1 (Unlimited)

Secondary Consideration Parameters:

Voltage - Clamping (Max) @ Ipp: 64.5V to 84V (acceptable range for 40V standoff class)
Current - Peak Pulse (10/1000µs): 6.2A to 48A (higher current ratings acceptable for same voltage class)
Power - Peak Pulse: 400W to 600W (higher power ratings acceptable)
Operating Temperature Range: -50°C to 175°C (must encompass or match original range)

All substitute parts listed maintain the 40V reverse standoff voltage specification and DO-214AC package format, ensuring direct functional and mechanical compatibility with the original SMAJ40 design.

Parameter Comparison

Part Number	Manufacturer	Voltage - Reverse Standoff (Typ)	Voltage - Breakdown (Min)	Voltage - Clamping (Max) @ Ipp	Current - Peak Pulse (10/1000µs)	Power - Peak Pulse	Operating Temperature	Package	Product Status
SMAJ40	Littelfuse Inc.	40V	42.08V	67.73V	6.2A	400W	-65 to 150°C (TJ)	DO-214AC, SMA	Obsolete
SMAJ40A	MDD	40V	44.4V	64.5V	6.2A	400W	-50 to 150°C (TJ)	DO-214AC, SMA	Active
SM4T47AY	STMicroelectronics	40V	44.4V	84V	27A (8/20µs)	400W	-55 to 150°C (TJ)	DO-214AC, SMA	Active
SMA6J40A-TR	STMicroelectronics	40V	44.4V	73.6V	48A (8/20µs)	600W	-55 to 175°C (TJ)	DO-214AC, SMA	Active
SMAJ40A-13-F	Diodes Incorporated	40V	44.4V	64.5V	6.2A	400W	-55 to 150°C (TJ)	DO-214AC, SMA	Active
SMAJ40A-TP	Micro Commercial Co	40V	44.4V	64.5V	6.2A	400W	-55 to 175°C (TA)	DO-214AC, SMA	Active
SMAJ40AE3/TR13	Microchip Technology	40V	44.4V	64.5V	7.8A	500W	-65 to 150°C (TJ)	DO-214AC, SMA	Active
SMAJ40E3/TR13	Microchip Technology	40V	44.4V	71.4V	7A	500W	-65 to 150°C (TJ)	DO-214AC, SMA	Active
TV04A400J-G	Comchip Technology	40V	44.4V	64.5V	6.2A	400W	-55 to 150°C (TJ)	DO-214AC, SMA	Active

Engineering Selection Recommendations

All listed substitute parts maintain active product status and ROHS3 compliance, ensuring long-term availability and regulatory conformance. Selection among substitutes should be based on the following criteria derived from provided specifications:

Direct Electrical Equivalents (Recommended for Drop-In Replacement): SMAJ40A (MDD), SMAJ40A-13-F (Diodes Incorporated), SMAJ40A-TP (Micro Commercial Co), and TV04A400J-G (Comchip Technology) provide identical electrical performance to the original SMAJ40, with matching 40V standoff voltage, 6.2A peak pulse current, and 400W power dissipation. These parts are suitable for direct substitution without circuit redesign.

Enhanced Performance Alternatives: SMAJ40AE3/TR13 (Microchip Technology) and SMAJ40E3/TR13 (Microchip Technology) offer increased peak pulse current (7.8A and 7A respectively) and higher power dissipation (500W), providing additional margin in overvoltage protection while maintaining the 40V standoff voltage specification. These are compatible substitutes for applications requiring enhanced transient suppression capability.

High-Current Applications: SMA6J40A-TR (STMicroelectronics) and SM4T47AY (STMicroelectronics) are suitable for circuits requiring higher peak pulse current handling (48A and 27A respectively) while maintaining the 40V standoff voltage. These parts are electrically compatible but provide enhanced surge protection capability.

Temperature Range Considerations: SMAJ40A-TP (Micro Commercial Co) and SMA6J40A-TR (STMicroelectronics) extend the upper operating temperature limit to 175°C, suitable for high-temperature environments. SMAJ40AE3/TR13 and SMAJ40E3/TR13 (Microchip Technology) maintain the original -65°C lower temperature limit, matching the SMAJ40 specification.

Frequently Asked Questions (FAQ)

Q: Can I use any of these substitute parts interchangeably with the SMAJ40? A: Yes, all listed parts are electrically and mechanically compatible substitutes. They maintain the 40V reverse standoff voltage, DO-214AC (SMA) package format, and unidirectional TVS diode configuration. Direct substitution is possible without circuit modification.

Q: What is the difference between the various SMAJ40A variants? A: The variants differ primarily in manufacturer and packaging format. SMAJ40A (MDD), SMAJ40A-13-F (Diodes Incorporated), SMAJ40A-TP (Micro Commercial Co), and TV04A400J-G (Comchip Technology) provide identical electrical specifications with 40V standoff, 6.2A peak pulse current, and 400W power dissipation. Selection can be based on supplier availability and packaging preference (Tape & Reel vs. bulk).

Q: Why do some substitutes have higher peak pulse current ratings? A: Higher current ratings (such as SMA6J40A-TR at 48A or SM4T47AY at 27A) provide additional transient suppression capability while maintaining the same 40V standoff voltage. These parts are suitable for applications experiencing higher-energy transient events and offer enhanced protection margin.

Q: Are all substitute parts RoHS3 compliant? A: Yes, all listed substitute parts are ROHS3 compliant and carry MSL 1 (Unlimited) moisture sensitivity rating, matching the original SMAJ40 environmental specifications.

Q: What is the significance of the clamping voltage variation across substitutes? A: Clamping voltage variations (64.5V to 84V) within the 40V standoff class are acceptable and do not affect substitution compatibility. The clamping voltage determines the maximum voltage spike suppression level; higher clamping voltages provide additional circuit protection margin.

Q: Can I use SMAJ40AE3/TR13 or SMAJ40E3/TR13 in place of the standard SMAJ40A? A: Yes, these Microchip Technology parts are fully compatible substitutes. They offer identical 40V standoff voltage with enhanced peak pulse current (7.8A and 7A respectively) and higher power dissipation (500W), making them suitable for applications requiring additional transient suppression capability.

Q: What packaging formats are available for these substitutes? A: All substitute parts are supplied in DO-214AC (SMA) surface-mount package format, matching the original SMAJ40. Packaging options include Tape & Reel (TR) for automated assembly and bulk formats depending on manufacturer and distributor availability.

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