1KSMB33 Equivalent & Substitute Parts

Part Overview

The 1KSMB33 is a unidirectional transient voltage suppressor (TVS) diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection in surface-mount applications. The device features a 28.2V reverse standoff voltage, 47.99V maximum clamping voltage, and 21.9A peak pulse current capability in a DO-214AA (SMB) package. The 1KSMB33 is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity.

Key Parameters

Parameter	Value	Unit
Voltage - Reverse Standoff (Typ)	28.2	V
Voltage - Breakdown (Min)	29.75	V
Voltage - Clamping (Max) @ Ipp	47.99	V
Current - Peak Pulse (10/1000µs)	21.9	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 1KSMB33 is determined by the following critical electrical and mechanical parameters:

Electrical Compatibility Criteria:

Reverse standoff voltage: 28.2V (nominal)
Breakdown voltage minimum: 29.75V or higher
Clamping voltage maximum: 47.99V or lower
Peak pulse current: 21.9A or higher
Peak pulse power: 1000W or higher
Unidirectional topology (single channel)

Mechanical Compatibility Criteria:

Package: DO-214AA (SMB) surface mount
Mounting type: Surface mount
Moisture sensitivity level: 1 (Unlimited)

Substitute parts are grouped into two categories based on electrical performance:

Category A - Full Electrical Equivalents (21.9A Peak Pulse Current): Parts maintaining the original 21.9A peak pulse current and 1000W power rating, suitable for direct replacement without circuit redesign.

Category B - Reduced Current Equivalents (13.0-13.3A Peak Pulse Current): Parts with lower peak pulse current (600W power rating) and reduced clamping voltage, suitable only where circuit design accommodates lower transient energy dissipation.

Parameter Comparison

Part Number	Manufacturer	Standoff Voltage (V)	Breakdown Min (V)	Clamp Max (V)	Peak Pulse Current (A)	Peak Power (W)	Temp Range (°C)	Status
1KSMB33	Littelfuse Inc.	28.2	29.75	47.99	21.9	1000	-55 to 150	Obsolete
1KSMB33A	Taiwan Semiconductor Corporation	28.2	31.4	45.7	21.9	1000	-55 to 175	Active
1KSMB33AH	Taiwan Semiconductor Corporation	28.2	31.4	45.7	21.9	1000	-55 to 175	Active
1KSMB33A M4G	Taiwan Semiconductor Corporation	28.2	31.4	45.7	21.9	1000	-55 to 175	Active
P6SMB33	Taiwan Semiconductor Corporation	26.8	29.7	47.7	13	600	-55 to 150	Active
P6SMB33A	Eaton - Electronics Division	28.2	31.4	45.7	13.3	600	-55 to 150	Active
P6SMB33A	Taiwan Semiconductor Corporation	28.2	31.4	45.7	13.3	600	-55 to 150	Active
P6SMB33A-E3/52	Vishay General Semiconductor - Diodes Division	28.2	31.4	45.7	13.1	600	-65 to 150	Active
P6SMB33A-E3/5B	Vishay General Semiconductor - Diodes Division	28.2	31.4	45.7	13.1	600	-65 to 150	Active
SZP6SMB33AT3G	Littelfuse Inc.	28.2	31.4	45.7	13.2	600	-65 to 150	Active

Engineering Selection Recommendations

Direct Replacement (Category A - Full Electrical Equivalents):

The 1KSMB33A series from Taiwan Semiconductor Corporation (standard, AH variant, and M4G variant) provides direct electrical and mechanical compatibility with the obsolete 1KSMB33. All three variants maintain 21.9A peak pulse current and 1000W power dissipation. The 1KSMB33A M4G variant is manufacturer-recommended. The 1KSMB33AH variant includes AEC-Q101 automotive qualification and extended temperature range (-55°C to 175°C), suitable for automotive and high-reliability applications.

Reduced Current Substitutes (Category B - Lower Power Rating):

The P6SMB33A series (Eaton, Taiwan Semiconductor Corporation, and Vishay variants) and SZP6SMB33AT3G (Littelfuse) operate at 13.0-13.3A peak pulse current with 600W power rating. These parts are suitable only where circuit design accommodates reduced transient energy dissipation. The Vishay P6SMB33A-E3/52 and P6SMB33A-E3/5B variants extend operating temperature to -65°C. The SZP6SMB33AT3G includes AEC-Q101 automotive qualification.

All substitute parts maintain RoHS3 compliance and MSL 1 (Unlimited) moisture sensitivity rating. All are available in DO-214AA (SMB) surface-mount packaging.

Frequently Asked Questions (FAQ)

Q: Can I use P6SMB33A parts as a direct replacement for 1KSMB33?

A: P6SMB33A parts are mechanically compatible but electrically reduced. They provide 13.3A peak pulse current versus the original 21.9A. Use only if circuit design accommodates 600W peak power instead of 1000W. Verify transient energy requirements before substitution.

Q: What is the difference between 1KSMB33A, 1KSMB33AH, and 1KSMB33A M4G?

A: All three maintain identical electrical specifications (28.2V standoff, 21.9A peak current, 1000W power). The 1KSMB33AH includes AEC-Q101 automotive qualification. The 1KSMB33A M4G is the manufacturer-recommended variant. Temperature range extends to -55°C to 175°C for both AH and M4G variants versus -55°C to 150°C for standard 1KSMB33A.

Q: Are all substitute parts available in the same DO-214AA (SMB) package?

A: Yes. All listed substitute parts use DO-214AA (SMB) surface-mount packaging, ensuring mechanical compatibility with the original 1KSMB33 PCB layout.

Q: Which substitute part is recommended for automotive applications?

A: The 1KSMB33AH (Taiwan Semiconductor Corporation) and SZP6SMB33AT3G (Littelfuse) both carry AEC-Q101 automotive qualification. The 1KSMB33AH maintains full electrical equivalence (21.9A), while SZP6SMB33AT3G operates at reduced current (13.2A).

Q: Do all substitute parts meet RoHS compliance?

A: Yes. All listed substitute parts are RoHS3 compliant with MSL 1 (Unlimited) moisture sensitivity rating.

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