1SMB5945 Equivalent & Substitute Parts

Part Overview

The 1SMB5945 is an active-status surface mount Zener diode rated for 68 V nominal voltage and 3 W maximum power dissipation in a DO-214AA (SMB) package. Manufactured by Taiwan Semiconductor Corporation, this component is RoHS3 compliant and suitable for voltage regulation and protection applications in electronic circuits. Substitute parts may be required due to inventory availability, supply chain constraints, or specific application requirements that demand alternative electrical or thermal characteristics within the allowed parameter ranges for this product category.

Substiute Parts

1SMB5945

Taiwan Semiconductor CorporationIn Stock: 8551SMB5945 Datasheet

Current PartRFQ

1SMB5945BT3G

onsemiIn Stock: 209251SMB5945BT3G Datasheet

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1SMB5944BT3G

onsemiIn Stock: 152421SMB5944BT3G Datasheet

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SMBJ5371B-TP

Micro Commercial CoIn Stock: 17580SMBJ5371B-TP Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the 1SMB5945 Zener diode is determined by the following critical parameters:

Direct Electrical Equivalence (Upgrade Category): The 1SMB5945BT3G manufactured by onsemi maintains identical nominal Zener voltage (68 V), tolerance (±5%), maximum power rating (3 W), impedance (120 Ohms), and reverse leakage current (1 µA @ 51.7 V). This part qualifies as a direct substitute with extended operating temperature range (-65°C to 150°C versus -55°C to 150°C). Both parts share the DO-214AA SMB package and RoHS3 compliance.

Similar Electrical Characteristics (Alternative Category): The 1SMB5944BT3G (onsemi) and SMBJ5371B-TP (Micro Commercial Co) represent alternative Zener diodes with differing voltage and power specifications. The 1SMB5944BT3G operates at 62 V nominal voltage with 3 W power rating, suitable for applications requiring lower voltage regulation. The SMBJ5371B-TP provides 60 V nominal voltage with elevated 5 W power dissipation capability, appropriate for higher thermal load scenarios. Both alternatives maintain surface mount SMB packaging and RoHS3 compliance but differ in voltage regulation point and thermal capacity.

Parameter Comparison

Engineering Selection Recommendations

Direct Substitution (1SMB5945BT3G): The 1SMB5945BT3G from onsemi is electrically and mechanically equivalent to the 1SMB5945. Both components maintain identical Zener voltage (68 V), power rating (3 W), impedance (120 Ohms), and reverse leakage specifications. The onsemi variant provides an extended lower operating temperature limit (-65°C versus -55°C), offering improved performance in cold environment applications. All regulatory compliance requirements (RoHS3, REACH Unaffected, EAR99) are satisfied. This part is suitable for direct replacement in existing designs without circuit modification.

Alternative Selection (1SMB5944BT3G): The 1SMB5944BT3G operates at 62 V nominal voltage, representing a 6 V reduction from the 1SMB5945 specification. This alternative is applicable only in applications where the lower voltage regulation point is acceptable. The 3 W power rating and SMB package remain consistent. Extended temperature range (-65°C to 150°C) is provided. Selection of this part requires circuit-level validation to confirm voltage tolerance compatibility.

Alternative Selection (SMBJ5371B-TP): The SMBJ5371B-TP from Micro Commercial Co operates at 60 V nominal voltage with elevated 5 W power dissipation capability. This part is suitable for applications requiring higher thermal capacity or where the 60 V regulation point is acceptable. The reduced impedance (40 Ohms versus 120 Ohms) and lower reverse leakage current (500 nA versus 1 µA) provide improved dynamic performance characteristics. Selection of this part requires confirmation that the lower voltage specification aligns with circuit requirements.

All substitute parts maintain active product status, RoHS3 compliance, and MSL Level 1 moisture sensitivity rating, ensuring compatibility with standard manufacturing and storage protocols.

Frequently Asked Questions (FAQ)

Q: Can the 1SMB5945BT3G be used as a direct replacement for the 1SMB5945?

A: Yes. The 1SMB5945BT3G maintains identical electrical specifications: 68 V nominal Zener voltage, ±5% tolerance, 3 W maximum power, 120 Ohms impedance, and 1 µA reverse leakage current at 51.7 V. Both components use the DO-214AA SMB package and are RoHS3 compliant. The onsemi variant provides extended lower temperature operation (-65°C versus -55°C).

Q: What is the difference between the 1SMB5945 and 1SMB5944BT3G?

A: The primary difference is the nominal Zener voltage: 1SMB5945 operates at 68 V, while 1SMB5944BT3G operates at 62 V. Both maintain 3 W power rating and SMB packaging. The 1SMB5944BT3G is suitable only for applications where 62 V voltage regulation is acceptable. Impedance differs slightly (100 Ohms versus 120 Ohms).

Q: When should the SMBJ5371B-TP be selected over the 1SMB5945?

A: The SMBJ5371B-TP is selected when higher power dissipation capacity (5 W versus 3 W) is required or when the 60 V nominal voltage specification aligns with circuit requirements. The lower impedance (40 Ohms) and reduced reverse leakage (500 nA) provide improved dynamic performance. This part is not suitable for applications requiring 68 V regulation.

Q: Are all substitute parts available in the same package?

A: Yes. All listed parts use the DO-214AA SMB surface mount package, ensuring mechanical compatibility with existing PCB layouts and assembly processes.

Q: Do all substitute parts meet the same compliance standards?

A: Yes. All parts are RoHS3 compliant, REACH unaffected, and classified as EAR99. All components have MSL Level 1 moisture sensitivity rating, permitting unlimited shelf life under standard storage conditions.

Q: What is the impedance significance in Zener diode selection?

A: Impedance (Zzt) affects the dynamic voltage regulation performance. Lower impedance values provide better voltage stability under varying load conditions. The 1SMB5945 and 1SMB5945BT3G both specify 120 Ohms, while the SMBJ5371B-TP provides 40 Ohms for improved regulation characteristics.

Q: Can operating temperature range differences affect part selection?

A: Yes. The 1SMB5945 operates from -55°C to 150°C, while both onsemi alternatives (1SMB5945BT3G and 1SMB5944BT3G) extend the lower limit to -65°C. Applications requiring operation below -55°C must use the extended-range variants. Upper temperature limits are identical across all parts.