SM8T40AH Equivalent & Substitute Parts

Part Overview

The SM8T40AH is an active Transient Voltage Suppressor (TVS) diode manufactured by Eaton - Electronics Division. This unidirectional zener device is designed for transient overvoltage protection in telecom applications. The part operates with a 40V reverse standoff voltage and provides 64.5V clamping at peak pulse current. The SM8T40AH is classified as Automotive grade with AEC-Q101 qualification and is supplied in DO-218AB (SMCJ) surface mount packaging.

Equivalent and substitute parts are identified to address component availability, supply chain continuity, or specific application requirements while maintaining electrical and mechanical compatibility within defined parameters.

Substiute Parts

SM8T40AH

Eaton - Electronics DivisionIn Stock: 729SM8T40AH Datasheet

Current PartRFQ

SLD8S40A

Littelfuse Inc.In Stock: 1290SLD8S40A Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the SM8T40AH are identified based on electrical parameter equivalence within the following criteria:

Electrical Compatibility Parameters:

• Voltage - Reverse Standoff (Typ): 40V
• Voltage - Clamping (Max) @ Ipp: 64.5V
• Voltage - Breakdown (Min): 44.4V
• Operating Temperature Range: -55°C to 175°C (TJ)
• Type: Unidirectional Zener
• Channels: 1

Mechanical & Compliance Parameters:

• Mounting Type: Surface Mount
• Grade: Automotive
• Qualification: AEC-Q101
• RoHS Status: ROHS3 Compliant
• Moisture Sensitivity Level: 1 (Unlimited)

The SLD8S40A from Littelfuse Inc. meets all electrical voltage and temperature specifications. Peak pulse current differs (108A versus 124A) and peak pulse power differs (7000W versus 8000W); however, both devices maintain the same clamping voltage and standoff voltage characteristics. Package form differs (SMTO-263 versus DO-218AB), requiring mechanical verification for board layout compatibility.

Parameter Comparison

Engineering Selection Recommendations

SM8T40AH Selection Criteria: The SM8T40AH is the primary reference part. It is active, Automotive grade, and AEC-Q101 qualified. The device provides 124A peak pulse current and 8000W peak pulse power in DO-218AB (SMCJ) packaging. This part is suitable for applications requiring maximum transient energy dissipation within the 40V standoff voltage class.

SLD8S40A Selection Criteria: The SLD8S40A from Littelfuse is an active, Automotive grade, AEC-Q101 qualified substitute. It maintains identical voltage specifications (40V standoff, 64.5V clamping) and temperature range (-55°C to 175°C). The device provides 108A peak pulse current and 7000W peak pulse power. The primary difference is packaging format (SMTO-263 versus DO-218AB). This substitute is applicable when the SMTO-263 package footprint is compatible with board design requirements and peak pulse current of 108A is sufficient for the application.

Both parts carry ROHS3 compliance, MSL 1 rating, and REACH unaffected status, meeting automotive and environmental regulatory requirements.

Frequently Asked Questions (FAQ)

Q: Can the SLD8S40A directly replace the SM8T40AH on a PCB designed for DO-218AB packaging?

A: No. The SLD8S40A uses SMTO-263 packaging while the SM8T40AH uses DO-218AB (SMCJ) packaging. These are different physical form factors with different footprints. PCB layout and land pattern modifications are required for substitution.

Q: Are the voltage specifications identical between SM8T40AH and SLD8S40A?

A: Yes. Both devices have 40V reverse standoff voltage (Typ), 44.4V breakdown voltage (Min), and 64.5V clamping voltage (Max) @ Ipp. They are electrically equivalent for voltage protection characteristics.

Q: What is the difference in peak pulse current between these two parts?

A: The SM8T40AH provides 124A peak pulse current while the SLD8S40A provides 108A peak pulse current. This represents a 16A difference. Applications requiring the full 124A capability must use the SM8T40AH.

Q: Are both parts qualified for automotive applications?

A: Yes. Both SM8T40AH and SLD8S40A are Automotive grade with AEC-Q101 qualification. Both meet automotive reliability and quality standards.

Q: Do both parts have the same operating temperature range?

A: Yes. Both devices operate from -55°C to 175°C (TJ), providing identical thermal performance specifications.

Q: What is the peak pulse power difference?

A: The SM8T40AH provides 8000W (8kW) peak pulse power while the SLD8S40A provides 7000W (7kW) peak pulse power. The SM8T40AH has 1000W additional dissipation capacity.

Q: Are both parts RoHS compliant?

A: Yes. Both SM8T40AH and SLD8S40A are ROHS3 compliant and carry MSL 1 (Unlimited) moisture sensitivity rating.

Q: Can I use SLD8S40A in a high-energy transient environment where 8kW dissipation is required?

A: No. The SLD8S40A is rated for 7000W peak pulse power. Applications requiring 8000W dissipation must use the SM8T40AH.