US1MFA Equivalent & Substitute Parts

Part Overview

The US1MFA is a general-purpose rectifier diode manufactured by onsemi, rated for 1000 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 This component is classified as "Not For New Designs," indicating it has been superseded in onsemi's product portfolio. Organizations using this diode in existing production or maintenance applications require equivalent alternatives that maintain electrical and mechanical compatibility while meeting current design standards and compliance requirements.

Substiute Parts

US1MFA

onsemiIn Stock: 17254US1MFA Datasheet

Current PartRFQ

AU1FM-M3/H

Vishay General Semiconductor - Diodes DivisionIn Stock: 8572AU1FM-M3/H Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the US1MFA is determined by strict equivalence across the following electrical and mechanical parameters:

Critical Matching Parameters:

• Voltage - DC Reverse (Vr) (Max): 1000 V
• Current - Average Rectified (Io): 1 A
• Reverse Recovery Time (trr): 75 ns
• Mounting Type: Surface Mount
• RoHS Compliance: ROHS3 Compliant
• Moisture Sensitivity Level: 1 (Unlimited)

Allowable Variation Parameters:

• Voltage - Forward (Vf) (Max) @ If: Within ±0.15 V tolerance
• Current - Reverse Leakage @ Vr: Lower values acceptable (improved performance)
• Capacitance @ Vr, F: Lower values acceptable (improved performance)
• Operating Temperature - Junction: Extended range acceptable
• Package / Case: Physically compatible surface mount packages

The AU1FM-M3/H meets all critical matching parameters and demonstrates improved performance characteristics in reverse leakage current and junction capacitance, while maintaining full electrical and mechanical compatibility.

Parameter Comparison

Engineering Selection Recommendations

The AU1FM-M3/H from Vishay General Semiconductor - Diodes Division is a direct functional equivalent to the US1MFA. Selection of this substitute is supported by the following engineering factors:

Compliance and Certification: Both components maintain ROHS3 compliance and REACH unaffected status, ensuring regulatory alignment for existing and new production environments.

Product Status: The AU1FM-M3/H carries an "Active" product status, providing long-term availability and supply chain stability compared to the US1MFA's "Not For New Designs" classification.

Electrical Performance: The AU1FM-M3/H demonstrates equivalent or superior electrical characteristics across all critical parameters. Forward voltage differential of 0.15 V at rated current falls within acceptable engineering tolerance for rectifier diode applications. Reverse leakage current is reduced by 80%, and junction capacitance is reduced by 45%, representing performance improvements that do not compromise circuit functionality.

Thermal Performance: Extended junction temperature range (-55°C to 175°C versus -55°C to 150°C) provides additional operational margin in high-temperature environments.

Package Compatibility: Both components utilize surface mount technology with physically compatible footprints suitable for standard PCB assembly processes.

Frequently Asked Questions (FAQ)

Q: Can the AU1FM-M3/H be used as a direct replacement for the US1MFA in existing circuit designs?

A: Yes. The AU1FM-M3/H meets all critical electrical parameters (1000 V reverse voltage, 1 A current rating, 75 ns recovery time) and maintains surface mount compatibility. The forward voltage difference of 0.15 V is within standard engineering tolerance for rectifier diode applications and does not affect circuit functionality.

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

A: The US1MFA specifies 1.7 V maximum forward voltage at 1 A, while the AU1FM-M3/H specifies 1.85 V at the same current. This 0.15 V difference represents approximately 9% variation and is acceptable for general-purpose rectification applications. Circuit designers should verify this parameter only if forward voltage drop is a critical design constraint.

Q: Are there package compatibility concerns when substituting these diodes?

A: The US1MFA uses SOD-123W packaging, while the AU1FM-M3/H uses DO-219AB (SMF) packaging. Both are surface mount packages with compatible footprints for standard PCB assembly. Physical dimensions and lead spacing are suitable for direct PCB layout substitution without redesign.

Q: Why does the AU1FM-M3/H have lower reverse leakage current?

A: The AU1FM-M3/H is classified as an avalanche diode technology, which exhibits superior reverse leakage characteristics (1 µA versus 5 µA at 1000 V). This represents improved performance and does not create compatibility issues in circuit applications.

Q: What is the impact of the lower junction capacitance in the AU1FM-M3/H?

A: The AU1FM-M3/H demonstrates 8.2 pF capacitance compared to 15 pF in the US1MFA. Lower capacitance improves high-frequency performance and reduces switching transients. This represents a performance improvement with no negative impact on circuit functionality.

Q: Are both components suitable for new design applications?

A: The US1MFA carries "Not For New Designs" status and should not be selected for new circuit development. The AU1FM-M3/H carries "Active" status and is appropriate for both new designs and replacement applications.

Q: Do both components meet current regulatory requirements?

A: Yes. Both the US1MFA and AU1FM-M3/H are ROHS3 compliant and REACH unaffected, meeting current environmental and regulatory standards for electronic component manufacturing and use.