1SMB40AT3G Equivalent & Substitute Parts

Part Overview

The 1SMB40AT3G is a unidirectional Transient Voltage Suppressor (TVS) diode manufactured by Littelfuse Inc., rated for 40V reverse standoff voltage with a 64.5V maximum clamping voltage. This component is designed for general-purpose transient voltage protection in surface-mount applications using the DO-214AA (SMB) package. The part is currently listed as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Key Parameters

Parameter	Value
Voltage - Reverse Standoff (Typ)	40V
Voltage - Breakdown (Min)	44.4V
Voltage - Clamping (Max) @ Ipp	64.5V
Current - Peak Pulse (10/1000µs)	9.3A
Power - Peak Pulse	600W
Package / Case	DO-214AA, SMB
Operating Temperature	-65°C ~ 150°C (TJ)
Mounting Type	Surface Mount
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitute parts for the 1SMB40AT3G are qualified based on the following critical parameters:

Voltage - Reverse Standoff (Typ): 40V
Voltage - Breakdown (Min): 44.4V
Voltage - Clamping (Max) @ Ipp: 64.5V
Current - Peak Pulse (10/1000µs): 9.3A (±tolerance acceptable)
Power - Peak Pulse: 600W
Package / Case: DO-214AA, SMB
Mounting Type: Surface Mount
RoHS Status: ROHS3 Compliant

All substitute parts listed maintain these electrical specifications within acceptable engineering tolerances and are available in the same surface-mount package configuration. Parts are grouped by manufacturer and product status (active vs. obsolete).

Parameter Comparison

Part Number	Manufacturer	VWM (V)	VBR (Min, V)	VC (Max, V)	Ipp (A)	Package	Status	Temp Range (°C)
1SMB40AT3G	Littelfuse Inc.	40	44.4	64.5	9.3	DO-214AA, SMB	Obsolete	-65 ~ 150
SMBJ40A	MDD	40	44.4	64.5	9.3	DO-214AA, SMB	Active	-50 ~ 150
SMBJ40A-HR	Littelfuse Inc.	40	44.4	64.5	9.3	DO-214AA, SMB	Active	-65 ~ 150
SMBJ40A-HRA	Littelfuse Inc.	40	44.4	64.5	9.3	DO-214AA, SMB	Active	-65 ~ 150
SM6T47AY	STMicroelectronics	40	44.4	84	48 (8/20µs)	DO-214AA, SMB	Active	-55 ~ 150
SMBJ40A-13-F	Diodes Incorporated	40	44.4	64.5	9.3	DO-214AA, SMB	Active	-55 ~ 150
SMBJ40A-TP	Micro Commercial Co	40	44.4	64.5	9.3	DO-214AA, SMB	Active	-55 ~ 175
SMBJ40A-TR	STMicroelectronics	40	44.4	64.5	9.7	DO-214AA, SMB	Active	-55 ~ 150
SMBJ40AE3/TR13	Microchip Technology	40	44.4	64.5	9.3	DO-214AA, SMB	Active	-65 ~ 150

Engineering Selection Recommendations

Primary Substitutes (Electrical and Thermal Match)

SMBJ40A-HR, SMBJ40A-HRA, and SMBJ40AE3/TR13 are direct electrical equivalents manufactured by Littelfuse Inc. and Microchip Technology. These parts maintain identical voltage ratings (40V standoff, 64.5V clamping) and current specifications (9.3A peak pulse). All are active products with ROHS3 compliance and MSL 1 rating. SMBJ40A-HR and SMBJ40A-HRA support the full temperature range of the original part (-65°C to 150°C).

Secondary Substitutes (Electrical Match with Temperature Considerations)

SMBJ40A (MDD), SMBJ40A-13-F (Diodes Incorporated), SMBJ40A-TP (Micro Commercial Co), and SMBJ40A-TR (STMicroelectronics) provide identical electrical performance with 40V standoff and 64.5V clamping specifications. These parts are active and ROHS3 compliant. Operating temperature ranges vary: MDD supports -50°C to 150°C, while Diodes Incorporated, Micro Commercial Co, and STMicroelectronics support -55°C to 150°C. SMBJ40A-TP extends to 175°C maximum junction temperature.

Alternative with Enhanced Performance (Higher Current Rating)

SM6T47AY (STMicroelectronics) maintains the 40V standoff and 44.4V minimum breakdown voltage but specifies 84V maximum clamping voltage and 48A peak pulse current (8/20µs pulse). This part is AEC-Q101 qualified for automotive applications and suitable for designs requiring higher transient current handling. Operating temperature range is -55°C to 150°C.

All substitute parts are available in DO-214AA (SMB) surface-mount package and maintain ROHS3 compliance and MSL 1 moisture sensitivity rating.

Frequently Asked Questions (FAQ)

Q: Can SMBJ40A-HR directly replace 1SMB40AT3G?

A: Yes. SMBJ40A-HR is manufactured by Littelfuse Inc. and provides identical electrical specifications: 40V reverse standoff, 44.4V minimum breakdown, 64.5V maximum clamping, and 9.3A peak pulse current. Both support -65°C to 150°C operating temperature and use DO-214AA (SMB) packaging. The part is active and ROHS3 compliant.

Q: What is the difference between SMBJ40A-HR and SMBJ40A-HRA?

A: Both parts are manufactured by Littelfuse Inc. with identical electrical specifications and temperature ranges (-65°C to 150°C). The suffix designations indicate different internal design or qualification variants. Both are suitable direct replacements for 1SMB40AT3G.

Q: Why does SM6T47AY have different clamping voltage and current ratings?

A: SM6T47AY is designed for higher transient current protection with 84V maximum clamping voltage and 48A peak pulse current (8/20µs). While it maintains the same 40V reverse standoff voltage, it is specified for applications requiring enhanced surge protection. This part is AEC-Q101 qualified for automotive use.

Q: Are all substitute parts available in the same package?

A: Yes. All substitute parts use DO-214AA (SMB) surface-mount package, ensuring mechanical and thermal compatibility with the original 1SMB40AT3G footprint.

Q: What is the temperature range difference between substitutes?

A: The original 1SMB40AT3G and primary substitutes (SMBJ40A-HR, SMBJ40A-HRA, SMBJ40AE3/TR13) support -65°C to 150°C. Secondary substitutes from other manufacturers support -50°C to -55°C minimum, with SMBJ40A-TP extending to 175°C maximum. Design requirements determine the appropriate selection.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All listed substitute parts are ROHS3 compliant with MSL 1 (unlimited) moisture sensitivity rating, matching the original part's environmental compliance.

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