SMS24T1 Equivalent & Substitute Parts

Part Overview

The SMS24T1 is a transient voltage suppressor (TVS) diode manufactured by onsemi, designed for general-purpose overvoltage protection in surface-mount applications. This component features a 24V reverse standoff voltage with a 44V maximum clamping voltage and 8A peak pulse current capability in an SC-74 package. The SMS24T1 is classified as obsolete, making identification of active equivalent and substitute parts essential for ongoing design support and procurement.

Key Parameters

Parameter	Value
Manufacturer Part Number	SMS24T1
Manufacturer	onsemi
Category	Transient Voltage Suppressors (TVS)
Type	Zener
Unidirectional Channels	4
Voltage - Reverse Standoff (Typ)	24V
Voltage - Clamping (Max) @ Ipp	44V
Current - Peak Pulse (8/20µs)	8A
Power - Peak Pulse	350W
Capacitance @ 1MHz	40pF
Operating Temperature	-55°C ~ 150°C (TJ)
Mounting Type	Surface Mount
Package / Case	SC-74, SOT-457
Product Status	Obsolete
RoHS Status	RoHS non-compliant

Substitute Part Grouping Explanation

Substitution of the SMS24T1 is determined by the following critical electrical and mechanical parameters:

Primary Substitution Criteria:

Reverse standoff voltage within the 24V specification
Clamping voltage performance at rated peak pulse current
Peak pulse current capability (8A minimum for direct replacement)
Unidirectional channel configuration (4 channels)
Surface-mount package compatibility (SC-74 / SOT-457)
Operating temperature range coverage

Substitute Categories:

Direct Equivalent (Identical Electrical Performance): SMS24T1G from onsemi provides identical electrical specifications with active product status and RoHS3 compliance. This part is the primary replacement for obsolete SMS24T1 units.

Partial Electrical Equivalents (Lower Performance Parameters): The BZA420A series (Nexperia) and BZA456A series (Nexperia) offer reduced peak pulse current and power dissipation compared to SMS24T1. BZA420A variants specify 20V reverse standoff with 28V clamping voltage. BZA456A variants specify 5.6V reverse standoff with 8V clamping voltage. These parts are suitable only for applications with lower voltage and current requirements than the original SMS24T1 specification.

Alternative with Enhanced Performance: PESD24VS4UD,115 from Nexperia provides 24V reverse standoff voltage matching SMS24T1, with enhanced clamping voltage (52V) and automotive-grade qualification (AEC-Q100). Peak pulse current is 4A, representing half the SMS24T1 capability.

Parameter Comparison

Parameter	SMS24T1	SMS24T1G	BZA420A,115	BZA420A,125	BZA420A,135	BZA420A,165	BZA456A,115	BZA456A,125	BZA456A,135	BZA456A,165	PESD24VS4UD,115
Manufacturer	onsemi	onsemi	Nexperia	Nexperia	Nexperia	Nexperia	Nexperia	Nexperia	Nexperia	Nexperia	Nexperia
Voltage - Reverse Standoff (Typ)	24V	24V	20V	20V	20V	20V	5.6V	5.6V	5.6V	5.6V	24V (Max)
Voltage - Clamping (Max) @ Ipp	44V	44V	28V	28V	28V	28V	8V	8V	8V	8V	52V
Current - Peak Pulse (8/20µs)	8A	8A	—	—	—	—	3A	3A	3A	3A	4A
Power - Peak Pulse	350W	350W	19.6W	19.6W	19.6W	19.6W	24W	24W	24W	24W	200W
Capacitance @ 1MHz	40pF	40pF	48pF	48pF	48pF	48pF	240pF	240pF	240pF	240pF	45pF
Operating Temperature	-55°C ~ 150°C (TJ)	-55°C ~ 150°C (TJ)	-65°C ~ 150°C (TJ)	-65°C ~ 150°C (TJ)	-65°C ~ 150°C (TJ)	-65°C ~ 150°C (TJ)	-65°C ~ 150°C (TJ)	-65°C ~ 150°C (TJ)	-65°C ~ 150°C (TJ)	-65°C ~ 150°C (TJ)	-65°C ~ 150°C (TA)
Unidirectional Channels	4	4	4	4	4	4	4	4	4	4	4
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Package / Case	SC-74, SOT-457	SC-74, SOT-457	SC-74, SOT-457	SC-74, SOT-457	SC-74, SOT-457	SC-74, SOT-457	SC-74, SOT-457	SC-74, SOT-457	SC-74, SOT-457	SC-74, SOT-457	SC-74, SOT-457
Product Status	Obsolete	Active	Active	Active	Active	Active	Active	Active	Active	Active	Active
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Automotive Grade	—	—	Yes (AEC-Q100)	Yes (AEC-Q100)	Yes (AEC-Q100)	Yes (AEC-Q100)	Yes (AEC-Q100)	Yes (AEC-Q100)	Yes (AEC-Q100)	Yes (AEC-Q100)	Yes (AEC-Q100)

Engineering Selection Recommendations

For Direct Replacement (Identical Electrical Performance): SMS24T1G is the primary active equivalent. This part maintains all electrical specifications of the obsolete SMS24T1 while offering active product status and ROHS3 compliance. Selection of SMS24T1G is appropriate for applications requiring no design modification and full electrical compatibility.

For RoHS3 Compliance with Automotive Qualification: PESD24VS4UD,115 provides 24V reverse standoff voltage matching the SMS24T1 specification with AEC-Q100 automotive qualification and ROHS3 compliance. The enhanced clamping voltage (52V versus 44V) and reduced peak pulse current (4A versus 8A) require circuit-level evaluation to confirm suitability. This part is suitable for automotive applications where compliance certifications are mandatory.

For Lower Voltage Applications: BZA420A series (20V reverse standoff, 28V clamping) and BZA456A series (5.6V reverse standoff, 8V clamping) are suitable only for applications with voltage requirements lower than the SMS24T1 specification. All Nexperia variants offer AEC-Q100 automotive qualification and ROHS3 compliance. Selection requires confirmation that reduced voltage and current ratings are acceptable for the target application.

Frequently Asked Questions (FAQ)

Q: Can SMS24T1G be used as a direct replacement for SMS24T1? A: Yes. SMS24T1G provides identical electrical specifications including 24V reverse standoff voltage, 44V clamping voltage, 8A peak pulse current, and 350W peak pulse power. Both parts use the SC-74 package. SMS24T1G is active and ROHS3 compliant, making it the recommended replacement for the obsolete SMS24T1.

Q: What is the difference between SMS24T1 and SMS24T1G? A: The primary differences are product status and RoHS compliance. SMS24T1 is obsolete and RoHS non-compliant. SMS24T1G is active and ROHS3 compliant. Electrical specifications are identical.

Q: Can BZA420A series parts replace SMS24T1? A: BZA420A series parts have lower electrical ratings (20V reverse standoff versus 24V, 28V clamping versus 44V, unspecified peak pulse current versus 8A). These parts are suitable only for applications with lower voltage and current requirements. Circuit-level evaluation is required to confirm compatibility.

Q: Can BZA456A series parts replace SMS24T1? A: BZA456A series parts have significantly lower electrical ratings (5.6V reverse standoff versus 24V, 8V clamping versus 44V, 3A peak pulse current versus 8A). These parts are not suitable for applications designed for 24V protection and are intended for lower voltage circuits.

Q: What is the advantage of PESD24VS4UD,115 over SMS24T1G? A: PESD24VS4UD,115 provides automotive-grade qualification (AEC-Q100) and enhanced clamping voltage (52V). However, peak pulse current is reduced to 4A. Selection depends on whether automotive qualification is required and whether the reduced current rating is acceptable for the application.

Q: Are all substitute parts available in the same SC-74 package? A: Yes. All listed substitute parts use SC-74 or SOT-457 package designations, providing mechanical compatibility with SMS24T1 PCB layouts.

Q: Do all substitute parts meet RoHS3 compliance? A: SMS24T1G and all Nexperia parts (BZA420A, BZA456A, PESD24VS4UD series) are ROHS3 compliant. The original SMS24T1 is RoHS non-compliant.

Q: Which substitute part has the widest operating temperature range? A: BZA420A, BZA456A, and PESD24VS4UD series all specify -65°C to 150°C operating temperature, which is wider than SMS24T1 (-55°C to 150°C).

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