STTH812G Equivalent & Substitute Parts

Part Overview

The STTH812G is a general-purpose rectifier diode manufactured by STMicroelectronics, rated for 1200 V DC reverse voltage with an 8 A average rectified current. The device is packaged in a D2PAK (TO-263-3) surface mount configuration and features fast recovery characteristics with a 100 ns reverse recovery time. This part is classified as obsolete, making identification of equivalent and substitute components necessary for ongoing design support, maintenance, and production continuity.

Substiute Parts

STTH812G

STMicroelectronicsIn Stock: 86169STTH812G Datasheet

Current PartRFQ

ISL9R18120S3ST

onsemiIn Stock: 1878ISL9R18120S3ST Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the STTH812G is determined by the following critical electrical and mechanical parameters:

Voltage Rating Compatibility: The substitute part must maintain the 1200 V DC reverse voltage specification to ensure safe operation within the original circuit design envelope.

Package Compatibility: The substitute part must use the D2PAK (TO-263-3) surface mount package to ensure mechanical and thermal compatibility with existing PCB layouts and thermal management designs.

Current Rating: While the substitute part may exceed the 8 A average rectified current specification, it must not fall below this threshold. Higher current ratings provide design margin and component availability flexibility.

Recovery Characteristics: The substitute part must maintain fast recovery characteristics (≤500 ns for currents >200 mA) to preserve circuit performance and switching behavior.

Compliance and Status: The substitute part must maintain RoHS3 compliance and preferably possess an active product status to ensure long-term availability and supply chain stability.

The ISL9R18120S3ST meets all substitution criteria while offering enhanced current capacity (18 A versus 8 A) and active product status.

Parameter Comparison

Engineering Selection Recommendations

For Obsolete Part Replacement: The ISL9R18120S3ST is the primary substitute for the STTH812G. Both devices maintain identical 1200 V reverse voltage ratings and D2PAK packaging, ensuring direct PCB compatibility. The substitute part holds active product status, providing assured long-term availability and supply chain continuity.

Compliance Alignment: Both the main part and substitute maintain ROHS3 compliance, REACH unaffected status, and MSL Level 1 (unlimited moisture sensitivity), ensuring regulatory and environmental compatibility across manufacturing and deployment environments.

Current Capacity Consideration: The ISL9R18120S3ST provides 18 A average rectified current capacity compared to the STTH812G's 8 A rating. This higher current capacity does not compromise circuit operation in applications designed for 8 A operation; it provides additional design margin and thermal performance headroom.

Thermal Management: Both parts specify a maximum junction operating temperature of 175°C. The substitute part extends the minimum operating temperature to -55°C, providing broader environmental operating range capability.

Frequently Asked Questions (FAQ)

Q: Can the ISL9R18120S3ST directly replace the STTH812G on existing PCBs?

A: Yes. Both devices use identical D2PAK (TO-263-3) surface mount packaging with the same pinout configuration (2 leads plus tab). No PCB layout modifications are required for mechanical or electrical connection.

Q: What is the impact of the higher 18 A current rating on circuit operation?

A: The higher current rating of the ISL9R18120S3ST does not negatively affect circuits designed for 8 A operation. The substitute part operates safely at or below its rated current. The increased capacity provides thermal margin and reduces junction temperature rise during operation.

Q: Are there differences in forward voltage drop between these parts?

A: Yes. The STTH812G exhibits 2.2 V forward voltage drop at 8 A, while the ISL9R18120S3ST exhibits 3.3 V forward voltage drop at 18 A. At equivalent current levels (8 A), the forward voltage characteristics differ due to different semiconductor technologies. Circuit designs with tight voltage regulation requirements should account for this difference.

Q: How do the reverse recovery times compare?

A: The STTH812G specifies 100 ns reverse recovery time, while the ISL9R18120S3ST specifies 300 ns. Both maintain fast recovery characteristics (≤500 ns). Applications sensitive to reverse recovery time performance should evaluate the 200 ns difference in switching behavior.

Q: Are both parts suitable for high-temperature applications?

A: Both parts specify 175°C maximum junction operating temperature. The ISL9R18120S3ST extends the minimum operating temperature to -55°C, providing broader environmental range. For applications operating at or near 175°C, thermal design and heat dissipation must be verified for both parts.

Q: What is the significance of the reverse leakage current difference?

A: The STTH812G specifies 8 µA reverse leakage at 1200 V, while the ISL9R18120S3ST specifies 100 µA. Applications with stringent leakage current requirements should evaluate this 92 µA difference. For most general-purpose rectification applications, this difference is not significant.

Q: Are there supply chain advantages to using the substitute part?

A: Yes. The ISL9R18120S3ST holds active product status with 1800 pieces in stock, while the STTH812G is classified as obsolete. The substitute part provides assured availability and long-term supply continuity for new designs and ongoing production requirements.