1KSMB30 Equivalent & Substitute Parts

Part Overview

The 1KSMB30 is a unidirectional Zener transient voltage suppressor (TVS) diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection in surface-mount applications. The device features a 25.6V reverse standoff voltage, 43.47V maximum clamping voltage, and 1000W peak pulse power rating in a DO-214AA (SMB) package. The 1KSMB30 is classified as obsolete, necessitating identification of active equivalent and substitute parts that maintain functional compatibility while meeting current supply chain requirements.

Key Parameters

Parameter	Value	Unit
Voltage - Reverse Standoff (Typ)	25.6	V
Voltage - Breakdown (Min)	27	V
Voltage - Clamping (Max) @ Ipp	43.47	V
Current - Peak Pulse (10/1000µs)	24.2	A
Power - Peak Pulse	1000	W
Operating Temperature Range	-55 to 150	°C
Package / Case	DO-214AA, SMB	—
Mounting Type	Surface Mount	—
Type	Zener	—
Unidirectional Channels	1	—

Substitute Part Grouping Explanation

Substitution of the 1KSMB30 is determined by the following critical electrical and mechanical parameters:

Voltage - Reverse Standoff (Typ): 25.6V
Voltage - Breakdown (Min): 27–28.5V range
Package / Case: DO-214AA, SMB (surface mount)
Mounting Type: Surface Mount
Type: Zener, Unidirectional
Operating Temperature: Minimum -55°C lower bound

Substitute parts are grouped into two categories based on power handling capability:

Category A - Full Power Equivalents (1000W): Parts maintaining the original 1000W peak pulse power rating with clamping voltages between 41.4V and 43.47V. These provide direct functional replacement with identical thermal performance.

Category B - Reduced Power Substitutes (600W): Parts with 600W peak pulse power rating and clamping voltages between 41.4V and 54.6V. These are suitable for applications where peak pulse power requirements do not exceed 600W and provide extended operating temperature ranges or automotive qualification in certain variants.

All substitute parts maintain the 25.6V reverse standoff voltage, DO-214AA/SMB package compatibility, and surface-mount configuration required for direct PCB replacement.

Parameter Comparison

Parameter	1KSMB30 (Main)	1KSMB30A	P6SMB30A	SZP6SMB30AT3G	SM6T30A-E3/52	SM6T30AY
Manufacturer	Littelfuse Inc.	Taiwan Semiconductor	Eaton - Electronics	Littelfuse Inc.	Vishay General Semiconductor	STMicroelectronics
Product Status	Obsolete	Active	Active	Active	Active	Active
Voltage - Reverse Standoff (Typ)	25.6V	25.6V	25.6V	25.6V	25.6V	25.6V
Voltage - Breakdown (Min)	27V	28.5V	28.5V	28.5V	28.5V	28.5V
Voltage - Clamping (Max) @ Ipp	43.47V	41.4V	41.4V	41.4V	41.5V	54.6V
Current - Peak Pulse (10/1000µs)	24.2A	24.2A	14.7A	14.4A	14.5A	75A (8/20µs)
Power - Peak Pulse	1000W	1000W	600W	600W	600W	600W
Operating Temperature Range	-55 to 150°C	-55 to 175°C	-55 to 150°C	-65 to 150°C	-65 to 150°C	-55 to 150°C
Package / Case	DO-214AA, SMB	DO-214AA, SMB	DO-214AA, SMB	DO-214AA, SMB	DO-214AA, SMB	DO-214AA, SMB
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Automotive Grade / AEC-Q101	—	—	—	Yes / AEC-Q101	—	Yes / AEC-Q101

Engineering Selection Recommendations

Primary Recommendation: 1KSMB30A (Taiwan Semiconductor Corporation)

The 1KSMB30A is the direct functional equivalent, maintaining the 1000W peak pulse power rating and 24.2A peak pulse current of the original 1KSMB30. This part is active in production, ROHS3 compliant, and offers an extended operating temperature range to 175°C. The clamping voltage of 41.4V is within acceptable tolerance for general-purpose TVS applications. This part provides the highest compatibility for direct PCB replacement without circuit redesign.

Secondary Recommendation: SM6T30A-E3/52 (Vishay General Semiconductor)

The SM6T30A-E3/52 is suitable for applications where 600W peak pulse power is acceptable. It maintains the 25.6V reverse standoff voltage and provides a clamping voltage of 41.5V. This part is ROHS3 compliant, active in production, and offers an extended lower operating temperature limit of -65°C. The TransZorb® series designation indicates proven reliability in general-purpose overvoltage protection.

Tertiary Recommendation: SZP6SMB30AT3G (Littelfuse Inc.)

The SZP6SMB30AT3G is recommended for automotive applications requiring AEC-Q101 qualification. It maintains the 25.6V reverse standoff voltage with a 41.4V clamping voltage and 600W peak pulse power rating. This part is ROHS3 compliant and offers an extended lower operating temperature limit of -65°C. The automotive-grade qualification makes it suitable for automotive and harsh-environment applications.

Not Recommended: P6SMB30A (Eaton - Electronics Division)

The P6SMB30A is not recommended due to RoHS non-compliance, which may conflict with regulatory requirements in many applications and supply chain policies.

Not Recommended: SM6T30AY (STMicroelectronics)

The SM6T30AY exhibits a significantly higher clamping voltage of 54.6V compared to the original 1KSMB30 (43.47V). While this part is automotive-grade and AEC-Q101 qualified, the elevated clamping voltage may exceed circuit protection thresholds and is suitable only for applications specifically designed for higher clamping voltages.

Frequently Asked Questions (FAQ)

Q: Can I use a 600W substitute part in place of the 1000W 1KSMB30?

A: Substitution depends on your circuit's peak pulse power requirements. If your application's transient energy does not exceed 600W, parts such as SM6T30A-E3/52, SZP6SMB30AT3G, or P6SMB30A are suitable. If peak pulse power exceeds 600W, only the 1KSMB30A maintains the original 1000W rating and is recommended.

Q: Are all substitute parts in the same package?

A: Yes. All substitute parts use the DO-214AA (SMB) surface-mount package, ensuring mechanical and PCB compatibility with the original 1KSMB30. Mounting footprints are identical.

Q: What is the significance of the clamping voltage differences?

A: The clamping voltage determines the maximum voltage the TVS diode allows across the protected circuit during a transient event. The 1KSMB30 clamps at 43.47V maximum. Substitute parts clamp between 41.4V and 54.6V. Lower clamping voltages (41.4–41.5V) provide tighter protection; higher clamping voltages (54.6V) allow higher transient voltages. Select based on your circuit's maximum allowable voltage specification.

Q: Which substitute part has the best availability?

A: SM6T30A-E3/52 (Vishay) has the highest inventory at 30,300 pieces. 1KSMB30A (Taiwan Semiconductor) has 9,100 pieces. Both are readily available for immediate procurement.

Q: Is RoHS compliance important for my application?

A: RoHS3 compliance is mandatory in most regulated markets and is increasingly required by OEMs and supply chain policies. The 1KSMB30A, SZP6SMB30AT3G, SM6T30A-E3/52, and SM6T30AY are all ROHS3 compliant. The P6SMB30A is RoHS non-compliant and should be avoided unless your application explicitly permits non-compliant components.

Q: Can I use an automotive-grade part in a non-automotive application?

A: Yes. Automotive-grade parts (SZP6SMB30AT3G and SM6T30AY) meet AEC-Q101 qualification and are suitable for any application. Automotive qualification indicates enhanced reliability testing and extended temperature performance, making these parts suitable for harsh-environment and mission-critical applications beyond automotive use.

Q: What is the difference between the 10/1000µs and 8/20µs pulse specifications?

A: These specify the transient pulse waveform used in testing. The 10/1000µs waveform (used by most substitutes) represents a faster rise-time transient; the 8/20µs waveform (SM6T30AY) represents a slower transient. Both are standard test conditions. The SM6T30AY's 75A rating at 8/20µs is not directly comparable to the 14.5A rating at 10/1000µs of other parts. Select based on your circuit's actual transient waveform characteristics.

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