SMAJ40C Equivalent & Substitute Parts

Part Overview

The SMAJ40C is a transient voltage suppressor (TVS) diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection in surface-mount applications. This bidirectional zener diode operates with a 40V reverse standoff voltage and provides 400W peak pulse power dissipation in a DO-214AC (SMA) package. The part is currently obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Substiute Parts

SMAJ40C

Littelfuse Inc.In Stock: 750SMAJ40C Datasheet

Current PartRFQ

SMAJ40CA

Good-Ark SemiconductorIn Stock: 19908SMAJ40CA Datasheet

DirectRFQ

SZ1SMA40CAT3G

Littelfuse Inc.In Stock: 2359SZ1SMA40CAT3G Datasheet

MFR RecommendedRFQ

SMAJ40CA

Good-Ark SemiconductorIn Stock: 19908SMAJ40CA Datasheet

DirectRFQ

SM4T47CAY

STMicroelectronicsIn Stock: 5380SM4T47CAY Datasheet

MFR RecommendedRFQ

SMAJ40CA-13-F

Diodes IncorporatedIn Stock: 18388SMAJ40CA-13-F Datasheet

MFR RecommendedRFQ

SMAJ40CA-TP

Micro Commercial CoIn Stock: 32122SMAJ40CA-TP Datasheet

MFR RecommendedRFQ

SMAJ40CA-TR

STMicroelectronicsIn Stock: 63124SMAJ40CA-TR Datasheet

MFR RecommendedRFQ

SMAJ40CAE3/TR13

Microchip TechnologyIn Stock: 5297SMAJ40CAE3/TR13 Datasheet

MFR RecommendedRFQ

SMAJ40CE3/TR13

Microchip TechnologyIn Stock: 808SMAJ40CE3/TR13 Datasheet

MFR RecommendedRFQ

TV04A400JB-G

Comchip TechnologyIn Stock: 1038TV04A400JB-G Datasheet

MFR RecommendedRFQ

TV04A400JB-HF

Comchip TechnologyIn Stock: 1072TV04A400JB-HF Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution for the SMAJ40C is determined by the following critical parameters:

• Reverse Standoff Voltage: 40V (Typ) — all substitutes must maintain this specification
• Package Type: DO-214AC (SMA) — mechanical and electrical compatibility requirement
• Bidirectional Configuration: Single channel, bidirectional operation
• Peak Pulse Power: 400W minimum (500W acceptable for higher current variants)
• Mounting Type: Surface mount only
• RoHS Compliance: ROHS3 Compliant

Substitute parts are grouped into two categories based on clamping voltage and peak pulse current characteristics:

Group A (Direct Electrical Equivalents): Parts with 64.5V clamping voltage and 6.2A peak pulse current. These provide the closest electrical match to the original SMAJ40C specification.

Group B (Higher Performance Variants): Parts with elevated clamping voltage (71.4V–84V) and increased peak pulse current (7A–27A). These offer enhanced transient suppression capability while maintaining the 40V standoff voltage and DO-214AC package compatibility.

Parameter Comparison

Engineering Selection Recommendations

Primary Substitutes (Direct Equivalents)

For applications requiring the closest electrical match to SMAJ40C specifications, select from the following active parts:

• SZ1SMA40CAT3G (Littelfuse Inc.): Maintains original manufacturer continuity with identical temperature range (-65°C ~ 150°C) and active product status. Includes AEC-Q101 automotive qualification.
• SMAJ40CAE3/TR13 (Microchip Technology): Offers enhanced performance with 7.8A peak pulse current and 500W power rating while preserving the 40V standoff voltage and -65°C ~ 150°C operating range.
• SMAJ40CA (Good-Ark Semiconductor): Cost-effective direct equivalent with 64.5V clamping voltage and 6.2A peak pulse current. Operating temperature limited to -55°C ~ 150°C.

Secondary Substitutes (Higher Performance Variants)

For applications where enhanced transient suppression is acceptable:

• SM4T47CAY (STMicroelectronics): Provides 27A peak pulse current and 84V clamping voltage with AEC-Q101 automotive qualification. Suitable for high-energy transient environments.
• SMAJ40CA-TR (STMicroelectronics): Equivalent to SM4T47CAY with identical electrical specifications and active status.
• SMAJ40CE3/TR13 (Microchip Technology): Intermediate performance option with 71.4V clamping voltage and 7A peak pulse current, maintaining -65°C ~ 150°C temperature range.

Temperature-Extended Option

• SMAJ40CA-TP (Micro Commercial Co): Extends upper operating temperature to 175°C (TA) while maintaining 64.5V clamping voltage and 6.2A peak pulse current. Suitable for high-temperature applications.

All recommended substitutes maintain ROHS3 compliance, DO-214AC (SMA) package compatibility, and bidirectional zener operation.

Frequently Asked Questions (FAQ)

Q: Can I use a substitute part with higher clamping voltage than the original SMAJ40C?

A: Yes. Parts with clamping voltages of 64.5V, 71.4V, or 84V are electrically compatible because they maintain the 40V reverse standoff voltage. Higher clamping voltage indicates stronger transient suppression capability. Verify that your circuit design tolerates the increased clamping voltage without affecting downstream components.

Q: What is the difference between 6.2A and 27A peak pulse current ratings?

A: Peak pulse current indicates the maximum transient current the TVS diode can suppress during a 10/1000µs pulse. Higher current ratings (27A) provide superior protection against high-energy transients. The 6.2A rating is sufficient for general-purpose applications; 27A variants are recommended for industrial or automotive environments with severe transient exposure.

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

A: Yes. All listed substitute parts use the DO-214AC (SMA) surface-mount package, ensuring mechanical and electrical compatibility with the original SMAJ40C footprint. Verify packaging specifications (Cut Tape, Tape & Reel, or Digi-Reel) match your procurement and assembly requirements.

Q: Why do some substitutes have different operating temperature ranges?

A: Operating temperature range depends on manufacturer design and qualification. The original SMAJ40C operates from -65°C to 150°C (TJ). Some substitutes are rated -55°C to 150°C (TJ), which is acceptable for most commercial applications. For extended low-temperature operation below -55°C, select SZ1SMA40CAT3G, SMAJ40CAE3/TR13, or SMAJ40CE3/TR13.

Q: Is RoHS compliance maintained across all substitute parts?

A: Yes. All listed substitute parts are ROHS3 compliant, matching the original SMAJ40C specification.

Q: What does "Bidirectional" mean for a TVS diode?

A: Bidirectional TVS diodes suppress transients in both positive and negative directions, protecting circuits from overvoltage events regardless of polarity. All listed parts maintain this single-channel bidirectional configuration.

Q: Can I substitute SMAJ40C with SM4T47CAY or SMAJ40CA-TR without circuit redesign?

A: These parts are pin-compatible and package-compatible. However, their 84V clamping voltage and 27A peak pulse current represent enhanced performance. Verify that your circuit design tolerates the lower clamping voltage threshold without affecting component protection strategy. No redesign is required for most general-purpose applications.