Equivalent & Substitute Parts for US1KFA

Part Overview

The US1KFA is a general-purpose rectifier diode manufactured by onsemi, rated for 800 V DC reverse voltage and 1 A average rectified current in a surface mount SOD-123FA package. This component is classified as "Not For New Designs," indicating it has been superseded in onsemi's product portfolio. Identifying equivalent and substitute parts is necessary for applications requiring continued sourcing, legacy system maintenance, or design flexibility across multiple suppliers while maintaining electrical and mechanical compatibility.

Substiute Parts

US1KFA

onsemiIn Stock: 15259US1KFA Datasheet

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AU1FK-M3/H

Vishay General Semiconductor - Diodes DivisionIn Stock: 18657AU1FK-M3/H Datasheet

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US1KAFC_R1_00001

Panjit International Inc.In Stock: 3935US1KAFC_R1_00001 Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the US1KFA are selected based on strict electrical and mechanical compatibility criteria. The primary substitution parameters are:

Electrical Compatibility:

• Voltage - DC Reverse (Vr) (Max): 800 V minimum
• Current - Average Rectified (Io): 1 A minimum
• Speed Classification: Fast Recovery ≤ 500ns, > 200mA (Io)
• Operating Temperature Range: Must encompass or exceed -55°C to 150°C

Mechanical Compatibility:

• Mounting Type: Surface Mount
• Package compatibility: SOD-123FA, DO-219AB, or SMAF-C packages

Compliance Requirements:

• RoHS3 Compliant
• MSL 1 (Unlimited)

The identified substitute parts meet these criteria with the following considerations:

AU1FK-M3/H (Vishay): Matches all electrical parameters with identical 800 V / 1 A ratings and 75 ns reverse recovery time. Extended operating temperature range (-55°C to 175°C). Different package (DO-219AB) requires PCB layout verification. Avalanche technology differs from standard technology but maintains functional equivalence.

US1KAFC_R1_00001 (Panjit): Matches all electrical parameters with identical 800 V / 1 A ratings. Reverse recovery time of 100 ns (slightly higher than 75 ns). Identical operating temperature range (-55°C to 150°C). SMAF-C package (DO-221AC with SMA Flat Leads) requires PCB footprint verification. Active product status supports long-term availability.

Parameter Comparison

Engineering Selection Recommendations

For Direct Replacement (Preferred):

US1KAFC_R1_00001 (Panjit) is the primary substitute when direct functional replacement is required. This part maintains identical electrical specifications (800 V / 1 A, 1.7 V forward voltage, -55°C to 150°C operating range) and identical product status classification (Active). The SMAF-C package footprint differs from SOD-123FA and requires PCB layout verification before implementation. This part is currently in active production status, supporting long-term design continuity.

For Extended Temperature Applications:

AU1FK-M3/H (Vishay) is suitable when operating temperature range extension to 175°C is beneficial. This part meets all electrical requirements with identical reverse recovery time (75 ns) and superior reverse leakage characteristics (1 µA versus 5 µA). The DO-219AB package differs from SOD-123FA and requires PCB footprint assessment. Avalanche technology classification differs from standard technology but maintains functional equivalence within specified electrical parameters.

Compliance Verification:

Both substitute parts maintain ROHS3 compliance, MSL 1 (Unlimited) rating, and EAR99 ECCN classification, matching the original US1KFA specifications. Both are suitable for applications requiring regulatory compliance with existing certifications.

Frequently Asked Questions (FAQ)

Q: Can US1KAFC_R1_00001 directly replace US1KFA on existing PCBs?

A: Electrical substitution is valid. However, the SMAF-C package (DO-221AC with SMA Flat Leads) has different physical dimensions and footprint compared to the SOD-123FA package. PCB layout verification is required before implementation. Consult package datasheets for dimensional specifications.

Q: What is the difference between the forward voltage specifications of these parts?

A: US1KFA and US1KAFC_R1_00001 both specify 1.7 V maximum forward voltage at 1 A. AU1FK-M3/H specifies 1.85 V maximum at 1 A. This 0.15 V difference is within typical rectifier diode tolerance and does not affect functional compatibility in most applications. Circuit design margins should account for this variation.

Q: Why does AU1FK-M3/H have lower reverse leakage current?

A: AU1FK-M3/H specifies 1 µA reverse leakage at 800 V, compared to 5 µA for US1KFA. This difference reflects manufacturing process variations between Vishay and onsemi. Both values are within acceptable ranges for general-purpose rectifier applications. Lower leakage may provide marginal benefits in high-impedance circuits.

Q: Are there package compatibility issues between these parts?

A: Yes. US1KFA uses SOD-123FA package, AU1FK-M3/H uses DO-219AB package, and US1KAFC_R1_00001 uses SMAF-C package (DO-221AC). These packages have different physical dimensions, lead configurations, and PCB footprints. Direct PCB substitution without layout modification is not possible. Footprint verification against manufacturer datasheets is mandatory.

Q: What is the significance of the "Not For New Designs" status on US1KFA?

A: This designation indicates onsemi has discontinued active development and recommends against using this part in new designs. Both substitute parts carry "Active" product status, indicating ongoing manufacturer support, production availability, and design continuity. For new applications, Active-status parts are preferred.

Q: How do reverse recovery time differences affect circuit performance?

A: US1KFA and AU1FK-M3/H both specify 75 ns reverse recovery time. US1KAFC_R1_00001 specifies 100 ns. This 25 ns difference is negligible in most rectifier applications operating below 100 kHz switching frequencies. High-frequency switching circuits (>500 kHz) should verify performance with actual reverse recovery time specifications.

Q: Are all three parts suitable for high-temperature applications?

A: US1KFA and US1KAFC_R1_00001 both specify -55°C to 150°C operating range. AU1FK-M3/H extends to -55°C to 175°C. For applications requiring operation above 150°C, AU1FK-M3/H is the appropriate selection. Standard circuit design practices should include thermal margin calculations.

Q: What packaging format differences exist between these parts?

A: US1KFA is supplied in Tape & Reel (TR) format. AU1FK-M3/H is supplied in Cut Tape (CT) format. US1KAFC_R1_00001 is supplied in Tape & Reel (TR) format. These differences affect procurement and assembly processes but do not impact electrical or mechanical performance of individual components.