SM4T35AY Equivalent & Substitute Parts

Part Overview

The SM4T35AY is a unidirectional transient voltage suppressor (TVS) diode manufactured by STMicroelectronics in the TRANSIL™ series. This surface mount component operates with a 30V reverse standoff voltage and 64.3V maximum clamping voltage, delivering 36A peak pulse current (8/20µs) in a compact DO-214AC (SMA) package. The device is qualified to AEC-Q101 automotive standards and maintains active product status with full RoHS3 compliance.

Equivalent and substitute parts are necessary when the primary part number becomes unavailable, when alternative packaging formats are required, or when sourcing from multiple manufacturers is strategically beneficial for supply chain resilience.

Key Parameters

Parameter	Value	Unit
Voltage - Reverse Standoff (Typ)	30	V
Voltage - Breakdown (Min)	33.3	V
Voltage - Clamping (Max) @ Ipp	64.3	V
Current - Peak Pulse (10/1000µs)	36	A (8/20µs)
Power - Peak Pulse	400	W
Package / Case	DO-214AC, SMA	—
Operating Temperature Range	-55 to 150	°C (TJ)
Type	Zener	—
Unidirectional Channels	1	—
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of TVS diodes is determined by electrical parameter compatibility within defined tolerance bands. The SM4T35AY operates with specific voltage and current characteristics that define its protective function in transient suppression circuits.

Primary substitution criteria:

Voltage - Reverse Standoff (Typ): 30V nominal
Voltage - Breakdown (Min): 33.3V minimum threshold
Package / Case: DO-214AC (SMA) form factor
Unidirectional topology: Single channel Zener type
RoHS3 compliance and MSL rating

Substitute parts are classified into two categories:

Direct Equivalent (Identical Electrical Performance): Parts with matching 64.3V clamping voltage and 36A peak pulse current, differing only in packaging format or manufacturer series designation.

Similar Equivalent (Reduced Performance Specification): Parts with matching 30V standoff voltage and DO-214AC package but lower clamping voltage (48.4V) and reduced peak pulse current (8.3A). These parts operate within the same voltage protection window but with reduced transient energy absorption capacity.

Parameter Comparison

Part Number	Manufacturer	Voltage - Reverse Standoff (V)	Voltage - Clamping (Max) @ Ipp (V)	Current - Peak Pulse (A)	Package	Product Status	Operating Temp (°C)
SM4T35AY	STMicroelectronics	30	64.3	36 (8/20µs)	DO-214AC, SMA	Active	-55 to 150
SMAJ30A-TR	STMicroelectronics	30	64.3	36 (8/20µs)	DO-214AC, SMA	Active	-55 to 150
PGSMAJ30AHR3G	Taiwan Semiconductor Corporation	30	48.4	8.3	DO-214AC, SMA	Obsolete	-55 to 175
SMAJ26A-TP	Micro Commercial Co	26	42.1	9.5	DO-214AC, SMA	Active	-55 to 175
SMAJ30A	MDD	30	48.4	8.3	DO-214AC, SMA	Active	-50 to 150
SMAJ30A-13-F	Diodes Incorporated	30	48.4	8.3	DO-214AC, SMA	Active	-55 to 150
SMAJ30A-E3/5A	Vishay General Semiconductor - Diodes Division	30	48.4	8.3	DO-214AC, SMA	Active	-55 to 150
SMAJ30A-E3/61	Vishay General Semiconductor - Diodes Division	30	48.4	8.3	DO-214AC, SMA	Active	-55 to 150
SMAJ30A-Q	Bourns Inc.	30	48.4	8.3	DO-214AC, SMA	Active	-55 to 150

Engineering Selection Recommendations

Direct Equivalent Selection:

SMAJ30A-TR (STMicroelectronics) is the direct electrical equivalent to SM4T35AY, offering identical voltage and current specifications with matching 64.3V clamping voltage and 36A peak pulse current. Both parts maintain active product status, AEC-Q101 qualification, and RoHS3 compliance. The primary distinction is packaging format: SMAJ30A-TR is supplied in Cut Tape (CT) & Digi-Reel® format versus SM4T35AY in Tape & Reel (TR). This substitution is appropriate for applications requiring identical transient suppression performance with alternative packaging logistics.

Similar Equivalent Selection:

Parts including SMAJ30A-13-F (Diodes Incorporated), SMAJ30A-E3/5A and SMAJ30A-E3/61 (Vishay), SMAJ30A (MDD), and SMAJ30A-Q (Bourns) share the 30V standoff voltage and DO-214AC package but operate with reduced clamping voltage (48.4V) and peak pulse current (8.3A). These parts are suitable for applications where the lower transient energy absorption capacity remains within circuit protection requirements. All similar equivalents maintain active product status and RoHS3 compliance.

PGSMAJ30AHR3G (Taiwan Semiconductor Corporation) carries obsolete product status and is not recommended for new designs despite matching voltage specifications.

SMAJ26A-TP (Micro Commercial Co) operates at 26V standoff voltage, representing a different voltage class and is not suitable as a direct substitute.

Frequently Asked Questions (FAQ)

Q: Can SMAJ30A-TR replace SM4T35AY in existing designs?

A: Yes. SMAJ30A-TR is a direct electrical equivalent with identical 30V standoff voltage, 64.3V clamping voltage, and 36A peak pulse current specifications. Both parts are manufactured by STMicroelectronics, maintain active product status, and carry AEC-Q101 automotive qualification. The substitution is valid for all electrical and thermal operating conditions specified for SM4T35AY.

Q: What is the difference between SM4T35AY and the SMAJ30A variants?

A: SM4T35AY belongs to the SM4TY series and delivers 36A peak pulse current with 64.3V clamping voltage. SMAJ30A variants from multiple manufacturers deliver 8.3A peak pulse current with 48.4V clamping voltage. Both share the 30V standoff voltage and DO-214AC package. The SMAJ30A variants provide lower transient energy absorption and are suitable only for applications with reduced transient stress requirements.

Q: Are all substitute parts qualified to AEC-Q101?

A: No. AEC-Q101 qualification is explicitly stated for SM4T35AY and SMAJ30A-Q (Bourns). Other substitute parts do not list AEC-Q101 qualification in the provided specifications. For automotive applications requiring AEC-Q101 compliance, selection must be limited to SM4T35AY or SMAJ30A-Q.

Q: What is the significance of packaging format differences (TR vs. CT)?

A: Tape & Reel (TR) and Cut Tape (CT) & Digi-Reel® represent different supply formats for surface mount components. TR format supplies components on continuous tape in reel form, while CT format supplies components on cut tape segments. Electrical performance is identical; packaging format selection depends on assembly equipment compatibility and procurement logistics.

Q: Can SMAJ26A-TP substitute for SM4T35AY?

A: No. SMAJ26A-TP operates at 26V standoff voltage, which is below the 30V specification of SM4T35AY. This voltage difference places it in a different protection class and makes it unsuitable as a substitute.

Q: Why is PGSMAJ30AHR3G listed as obsolete?

A: PGSMAJ30AHR3G carries obsolete product status, indicating it is no longer in active production or support. Obsolete parts present supply chain risk and are not recommended for new designs or ongoing production applications.

Q: What operating temperature range should be considered for substitution?

A: SM4T35AY operates from -55°C to 150°C (TJ). Most substitute parts maintain this range. PGSMAJ30AHR3G and SMAJ26A-TP extend to 175°C, providing wider thermal operating margin. MDD SMAJ30A operates from -50°C to 150°C, which is slightly narrower at the lower temperature limit. Substitution is valid when the substitute part's operating temperature range encompasses the application's thermal requirements.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All substitute parts listed carry RoHS3 compliance status, matching the environmental compliance requirement of SM4T35AY.

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