SMA4F24AY Equivalent & Substitute Parts

Part Overview

The SMA4F24AY is a unidirectional Transient Voltage Suppressor (TVS) diode manufactured by STMicroelectronics, designed for surface mount applications in automotive-grade circuits. This component operates with a 24V reverse standoff voltage and provides transient protection with a maximum clamping voltage of 38.9V at peak pulse current. The part is classified as Last Time Buy, indicating discontinued production status. Identification of equivalent and substitute parts is necessary to ensure design continuity, maintain supply chain reliability, and support long-term product availability for applications requiring TVS protection in automotive environments.

Substiute Parts

SMA4F24AY

STMicroelectronicsIn Stock: 5642SMA4F24AY Datasheet

Current PartRFQ

SM4T28AY

STMicroelectronicsIn Stock: 15649SM4T28AY Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the SMA4F24AY is determined by the following critical electrical and mechanical parameters:

Voltage Parameters: The reverse standoff voltage (24V typical) and breakdown voltage minimum (26.7V) establish the protection threshold. Substitute parts must maintain these voltage specifications to ensure proper circuit protection activation.

Current Handling: Peak pulse current rating determines the transient energy absorption capability. The SMA4F24AY handles 10.3A at 10/1000µs pulse duration with 400W peak pulse power dissipation.

Clamping Voltage: The maximum clamping voltage of 38.9V defines the voltage ceiling during transient suppression. This parameter directly impacts downstream component protection.

Package and Mounting: Surface mount configuration with DO-221AC SMA Flat Leads packaging establishes the physical form factor requirement.

Automotive Compliance: AEC-Q101 qualification and automotive grade classification are mandatory for applications requiring automotive-level reliability and traceability.

Operating Temperature: The -55°C to 175°C junction temperature range specifies thermal performance boundaries.

The SM4T28AY substitute maintains compatibility across voltage standoff, breakdown, automotive grade, AEC-Q101 qualification, surface mount configuration, and MSL rating. Differences in clamping voltage (50V vs. 38.9V), peak pulse current (46A vs. 10.3A at different pulse duration), operating temperature maximum (150°C vs. 175°C), and package variant (DO-214AC SMA vs. DO-221AC SMA Flat Leads) represent measurable deviations that must be evaluated within specific application requirements.

Parameter Comparison

Engineering Selection Recommendations

Product Status Consideration: The SMA4F24AY is designated Last Time Buy, indicating end-of-life status with no future production. The SM4T28AY maintains Active product status, ensuring ongoing availability and supply chain continuity.

Compliance and Certification: Both parts carry identical automotive-grade classification and AEC-Q101 qualification, meeting automotive industry reliability and traceability requirements. Both components maintain REACH Unaffected status and EAR99 ECCN classification.

Electrical Parameter Alignment: Both parts share identical reverse standoff voltage (24V) and breakdown voltage minimum (26.7V), establishing equivalent protection activation thresholds. The SM4T28AY exhibits higher clamping voltage (50V vs. 38.9V) and higher peak pulse current capability (46A vs. 10.3A), representing enhanced transient suppression capacity.

Temperature Operating Range: The SMA4F24AY supports junction temperatures to 175°C, while the SM4T28AY operates to 150°C maximum. Applications requiring operation above 150°C junction temperature require retention of the original part or identification of alternative substitutes.

Package Compatibility: The SMA4F24AY uses DO-221AC SMA Flat Leads packaging, while the SM4T28AY uses DO-214AC SMA packaging. Physical board layout and footprint compatibility must be verified before substitution.

Inventory and Supply: The SM4T28AY demonstrates higher current inventory levels (15,600 pcs vs. 5,540 pcs), supporting improved supply availability for new designs and production continuity.

Frequently Asked Questions (FAQ)

Q: Can the SM4T28AY directly replace the SMA4F24AY in existing designs?

A: Direct replacement requires verification of three factors: (1) PCB footprint compatibility between DO-221AC SMA Flat Leads and DO-214AC SMA packages, (2) circuit tolerance for the higher clamping voltage (50V vs. 38.9V), and (3) application operating temperature requirements not exceeding 150°C junction temperature. Electrical protection thresholds remain equivalent due to matching reverse standoff and breakdown voltages.

Q: What are the key differences in transient suppression performance?

A: The SM4T28AY provides higher peak pulse current handling (46A at 8/20µs vs. 10.3A at 10/1000µs) and higher clamping voltage (50V vs. 38.9V). Both maintain 400W peak pulse power dissipation. The higher clamping voltage in the substitute may result in slightly higher voltage stress on protected components during transient events.

Q: Are both parts suitable for automotive applications?

A: Yes. Both the SMA4F24AY and SM4T28AY carry automotive-grade classification and AEC-Q101 qualification, meeting automotive industry standards for reliability, traceability, and environmental performance.

Q: What is the significance of the Last Time Buy status for the SMA4F24AY?

A: Last Time Buy designation indicates that STMicroelectronics has discontinued production of the SMA4F24AY and will not manufacture additional units beyond existing inventory. This status necessitates identification of substitute parts for long-term design support and production continuity.

Q: How do the package differences affect PCB design?

A: The SMA4F24AY uses DO-221AC SMA Flat Leads packaging, while the SM4T28AY uses DO-214AC SMA packaging. These represent different physical form factors with distinct footprint dimensions. PCB layout modifications may be required to accommodate the substitute package, including potential changes to solder pad geometry and component placement.

Q: Can the SM4T28AY be used in applications with junction temperatures above 150°C?

A: No. The SM4T28AY maximum junction temperature rating is 150°C, compared to 175°C for the SMA4F24AY. Applications requiring sustained operation above 150°C junction temperature require retention of the original part or identification of alternative substitutes with higher temperature ratings.

Q: What is the impact of different pulse duration specifications?

A: The SMA4F24AY specifies peak pulse current at 10/1000µs pulse duration, while the SM4T28AY specifies 46A at 8/20µs pulse duration. These represent different transient event profiles. The 8/20µs waveform is commonly used for lightning and surge testing, while 10/1000µs represents a different transient characteristic. Application-specific transient profiles must be evaluated to determine substitution suitability.