STTH312B-TR Equivalent & Substitute Parts

Part Overview

The STTH312B-TR is a general-purpose rectifier diode manufactured by STMicroelectronics, rated for 1200 V DC reverse voltage with 3 A average rectified current in a Surface Mount DPAK package. This component is classified as Obsolete, indicating discontinuation from the manufacturer. Identifying equivalent and substitute parts is necessary to maintain design continuity, ensure supply chain availability, and support ongoing production requirements for applications utilizing this diode specification.

Substiute Parts

STTH312B-TR

STMicroelectronicsIn Stock: 16349STTH312B-TR Datasheet

Current PartRFQ

RURD4120S9A-F085

onsemiIn Stock: 30227RURD4120S9A-F085 Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the STTH312B-TR is determined by electrical and mechanical compatibility across the following critical parameters:

Voltage Rating: The substitute part must maintain the 1200 V DC reverse voltage specification to ensure equivalent circuit protection and reliability in the target application.

Current Rating: The substitute part current rating must equal or exceed the 3 A average rectified current requirement. Parts with higher current ratings (4 A) are acceptable as they provide additional design margin without compromising circuit function.

Forward Voltage Characteristics: Forward voltage drop at rated current must be comparable to ensure equivalent power dissipation and thermal performance. Variations within 0.1 V are acceptable within the specified current range.

Recovery Speed: Fast recovery classification (≤ 500ns, > 200mA) is maintained across substitute parts to preserve switching performance and minimize reverse recovery losses.

Package Compatibility: The substitute part must utilize the same Surface Mount DPAK package (TO-252-3, SC-63) to ensure mechanical fit and thermal interface compatibility with existing PCB designs.

Compliance Standards: RoHS3 compliance and MSL Level 1 rating are maintained across all substitute parts to meet regulatory and manufacturing requirements.

Parameter Comparison

Engineering Selection Recommendations

The RURD4120S9A-F085 from onsemi is a direct substitute for the obsolete STTH312B-TR. The substitute part meets or exceeds all critical electrical parameters: equivalent 1200 V reverse voltage rating, higher 4 A current rating providing design margin above the 3 A requirement, comparable forward voltage characteristics, and identical fast recovery speed classification. Both parts share identical Surface Mount DPAK packaging, ensuring mechanical and thermal compatibility with existing PCB layouts.

The substitute part is currently in Active production status, providing reliable long-term supply availability compared to the Obsolete status of the main part. Both components maintain ROHS3 compliance and MSL Level 1 rating, satisfying regulatory and manufacturing requirements.

The RURD4120S9A-F085 incorporates Avalanche technology with AEC-Q101 automotive qualification, offering enhanced overvoltage protection characteristics beyond the Standard technology of the original part. The faster reverse recovery time (90 ns versus 115 ns) and higher reverse leakage current (100 µA versus 10 µA) are acceptable trade-offs for general-purpose rectification applications and do not compromise circuit performance within the specified operating parameters.

Frequently Asked Questions (FAQ)

Q: Can the RURD4120S9A-F085 be used as a direct replacement for the STTH312B-TR in existing designs?

A: Yes. Both parts share identical 1200 V reverse voltage rating, Surface Mount DPAK package, and fast recovery speed classification. The substitute part's higher 4 A current rating and faster recovery time provide equivalent or improved performance for the 3 A application requirement.

Q: What is the significance of the higher current rating (4 A) on the substitute part?

A: The 4 A rating on the RURD4120S9A-F085 exceeds the 3 A requirement of the original application, providing additional design margin and thermal headroom. This does not create compatibility issues; the part operates safely at the lower current level.

Q: Are the package dimensions identical between the two parts?

A: Yes. Both the STTH312B-TR and RURD4120S9A-F085 utilize the TO-252-3 DPAK package (SC-63), ensuring identical PCB footprint, lead spacing, and thermal interface characteristics.

Q: What is the difference between Standard and Avalanche technology in these diodes?

A: The STTH312B-TR uses Standard technology, while the RURD4120S9A-F085 uses Avalanche technology. Avalanche technology provides enhanced overvoltage protection through controlled breakdown characteristics, offering additional reliability in transient overvoltage conditions without affecting normal rectification performance.

Q: Does the faster reverse recovery time (90 ns vs. 115 ns) affect circuit compatibility?

A: No. Faster reverse recovery time reduces reverse recovery losses and improves switching performance. This characteristic is beneficial and does not create compatibility issues with existing circuit designs.

Q: Why is the reverse leakage current higher on the substitute part (100 µA vs. 10 µA)?

A: The higher reverse leakage current on the RURD4120S9A-F085 is within acceptable limits for general-purpose rectification applications and does not compromise circuit function. Both values remain negligible relative to the forward current ratings.

Q: Are both parts RoHS compliant?

A: Yes. Both the STTH312B-TR and RURD4120S9A-F085 are ROHS3 compliant and carry MSL Level 1 (Unlimited) moisture sensitivity rating, meeting regulatory and manufacturing requirements.

Q: What is the advantage of AEC-Q101 qualification on the substitute part?

A: AEC-Q101 qualification indicates the RURD4120S9A-F085 meets automotive industry reliability and quality standards. This qualification provides additional assurance of component reliability and consistency, beneficial for applications requiring enhanced quality documentation.