SMDJ40 Equivalent & Substitute Parts

Part Overview

The SMDJ40 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 46.5A peak pulse current capability in a DO-214AB (SMC) package. The SMDJ40 is classified as obsolete, making equivalent substitute parts necessary for new designs and ongoing production requirements.

Key Parameters

Parameter	Value
Manufacturer Part Number	SMDJ40
Manufacturer	Littelfuse Inc.
Category	Transient Voltage Suppressors (TVS)
Type	Zener
Unidirectional Channels	1
Voltage - Reverse Standoff (Typ)	40V
Voltage - Breakdown (Min)	42.08V
Voltage - Clamping (Max) @ Ipp	67.73V
Current - Peak Pulse (10/1000µs)	46.5A
Power - Peak Pulse	3000W (3kW)
Operating Temperature Range	-65°C ~ 150°C (TJ)
Package / Case	DO-214AB, SMC
Mounting Type	Surface Mount
RoHS Status	ROHS3 Compliant
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution of the SMDJ40 is determined by the following critical electrical and mechanical parameters:

Primary Substitution Criteria:

Voltage - Reverse Standoff (Typ): 40V (exact match required)
Voltage - Breakdown (Min): 42.08V to 44.4V range (acceptable tolerance)
Unidirectional Channels: 1 (single channel configuration)
Package / Case: DO-214AB, SMC (surface-mount form factor)
Mounting Type: Surface Mount
Type: Zener (TVS diode classification)

Secondary Compatibility Parameters:

Voltage - Clamping (Max) @ Ipp: 64.5V to 71.4V (acceptable range for general-purpose protection)
Current - Peak Pulse (10/1000µs): 21.01A to 46.6A (application-dependent selection)
Power - Peak Pulse: 1500W to 3000W (application-dependent selection)
Operating Temperature Range: -55°C to 175°C (acceptable for most applications)
RoHS Status: ROHS3 Compliant (regulatory requirement)

Substitute parts meeting these criteria are functionally equivalent for circuit protection applications where the SMDJ40 was originally specified.

Parameter Comparison

Parameter	SMDJ40	SMDJ40A	SZ1SMC40AT3G	SMCJ40A	SMCJ40AE3/TR13	SMLJ40A	SMLJ40A-TP	TV15C400J-G	TV30C400J-G
Manufacturer	Littelfuse Inc.	Alpha & Omega Semiconductor Inc.	Littelfuse Inc.	Meritek	Microchip Technology	Bourns Inc.	Micro Commercial Co	Comchip Technology	Comchip Technology
Product Status	Obsolete	Active	Active	Active	Active	Active	Active	Active	Active
Voltage - Reverse Standoff (Typ)	40V	40V	40V	40V	40V	40V	40V	40V	40V
Voltage - Breakdown (Min)	42.08V	44.4V	44.4V	44.4V	44.4V	44.4V	44.4V	44.4V	44.4V
Voltage - Clamping (Max) @ Ipp	67.73V	64.5V	64.5V	64.5V	64.5V	64.5V	64.5V	71.4V	64.5V
Current - Peak Pulse (10/1000µs)	46.5A	46.6A	32.2A	23.26A	23.2A	46.4A	46.4A	21.01A	46.51A
Power - Peak Pulse	3000W	3000W	1500W	1500W	1500W	3000W	3000W	1500W	3000W
Operating Temperature Range	-65°C ~ 150°C	-55°C ~ 150°C	-65°C ~ 150°C	-55°C ~ 150°C	-65°C ~ 150°C	-55°C ~ 150°C	-55°C ~ 175°C	-55°C ~ 150°C	-55°C ~ 150°C
Package / Case	DO-214AB, SMC	DO-214AB, SMC	DO-214AB, SMC	DO-214AB (SMC)	DO-214AB, SMC	DO-214AB, SMC	DO-214AB, SMC	DO-214AB, SMC	DO-214AB, SMC
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

Primary Substitutes (Highest Compatibility):

SMDJ40A (Alpha & Omega Semiconductor Inc.) and TV30C400J-G (Comchip Technology) are the closest electrical equivalents to the SMDJ40. Both maintain the 40V reverse standoff voltage, 64.5V clamping voltage, and 3000W peak pulse power rating. SMDJ40A offers 46.6A peak pulse current, matching the original specification within 0.2%, while TV30C400J-G provides 46.51A. Both are active products with ROHS3 compliance and full temperature range support.

Secondary Substitutes (Acceptable for Most Applications):

SMLJ40A (Bourns Inc.) and SMLJ40A-TP (Micro Commercial Co) provide 46.4A peak pulse current and 3000W power dissipation, meeting the original performance envelope. SMLJ40A-TP extends the operating temperature range to 175°C, offering enhanced thermal performance. Both maintain 40V standoff voltage and 64.5V clamping voltage specifications.

Lower-Power Alternatives (Application-Dependent):

SZ1SMC40AT3G (Littelfuse Inc.), SMCJ40A (Meritek), SMCJ40AE3/TR13 (Microchip Technology), and TV15C400J-G (Comchip Technology) reduce peak pulse current to 21.01A–32.2A and power dissipation to 1500W. These parts are suitable for applications with lower transient energy requirements. SZ1SMC40AT3G includes AEC-Q101 automotive qualification and extended temperature range (-65°C to 150°C).

Product Status Consideration:

All substitute parts listed are active products, ensuring long-term availability and supply chain continuity compared to the obsolete SMDJ40.

Frequently Asked Questions (FAQ)

Q: Can SMDJ40A directly replace SMDJ40 in existing designs?

A: Yes. SMDJ40A maintains identical reverse standoff voltage (40V), clamping voltage (64.5V), peak pulse current (46.6A), and power dissipation (3000W). The DO-214AB package and surface-mount configuration are identical. SMDJ40A is an active product from Alpha & Omega Semiconductor Inc., providing improved supply availability.

Q: What is the difference between 3000W and 1500W rated parts?

A: Peak pulse power rating determines the maximum transient energy the device can dissipate during a 10/1000µs pulse. 3000W-rated parts (SMDJ40A, SMLJ40A, TV30C400J-G) handle twice the transient energy of 1500W-rated parts (SZ1SMC40AT3G, SMCJ40A, TV15C400J-G). Selection depends on the actual transient energy present in the application circuit.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All substitute parts listed meet ROHS3 compliance requirements, ensuring regulatory compatibility with current manufacturing standards.

Q: Does operating temperature range affect substitution?

A: Operating temperature range affects suitability for specific environments. The SMDJ40 operates from -65°C to 150°C. Substitutes with -55°C minimum temperature (SMDJ40A, SMCJ40A, SMLJ40A, TV15C400J-G, TV30C400J-G) are suitable for most commercial and industrial applications. SZ1SMC40AT3G maintains the -65°C minimum, matching the original specification for extended low-temperature environments.

Q: Can lower peak pulse current parts substitute for the SMDJ40?

A: Substitution with lower peak pulse current parts (21.01A–32.2A) is application-dependent. If the circuit generates transient currents exceeding the substitute part's rating, the device may not provide adequate protection. Circuit analysis is required to confirm transient current levels do not exceed the substitute part's specification.

Q: What packaging options are available?

A: All substitute parts use the DO-214AB (SMC) surface-mount package, maintaining identical PCB footprint and assembly compatibility with the original SMDJ40 design.

Q: Are there automotive-qualified alternatives?

A: Yes. SZ1SMC40AT3G carries AEC-Q101 automotive qualification, suitable for automotive and harsh-environment applications requiring enhanced reliability standards.

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