SCR74B-121 Equivalent & Substitute Parts

Part Overview

The SCR74B-121 is a 120 µH shielded surface mount inductor manufactured by Signal Transformer, rated for 1.08 A continuous current with a maximum DC resistance of 680mOhm. This component is classified as obsolete, making identification of functionally equivalent alternatives necessary for ongoing design support and procurement continuity.

Substiute Parts

SCR74B-121

Signal TransformerIn Stock: 979SCR74B-121 Datasheet

Current PartRFQ

74404084121

Würth ElektronikIn Stock: 263274404084121 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the SCR74B-121 is based on the following critical parameters:

• Inductance Value: 120 µH with ±20% tolerance
• Current Rating: Minimum 1.08 A continuous current capability
• DC Resistance: Maximum 680mOhm to maintain circuit performance
• Operating Temperature: -40°C ~ 125°C compatibility
• Mounting Configuration: Surface mount, nonstandard package footprint
• Regulatory Compliance: ROHS3 compliance required

The substitute part 74404084121 (Würth Elektronik WE-LQS series) meets these substitution criteria with equivalent inductance, superior current rating (1.15 A), lower DC resistance (347mOhm), and identical temperature range operation.

Parameter Comparison

Engineering Selection Recommendations

The 74404084121 (Würth Elektronik WE-LQS) is the qualified substitute for the obsolete SCR74B-121. Selection is based on:

• Electrical Equivalence: Identical 120 µH inductance value with matching ±20% tolerance and identical operating temperature range
• Current Capability: The substitute provides 1.15 A rating, exceeding the 1.08 A requirement of the original part
• Resistance Performance: DC resistance of 347mOhm is significantly lower than the 680mOhm maximum of the original, providing improved efficiency
• Regulatory Compliance: Both parts maintain ROHS3 compliance and REACH unaffected status
• Product Status: The substitute is active production, ensuring long-term availability and supply chain continuity
• Quality Certification: The substitute carries AEC-Q200 automotive qualification, providing additional reliability assurance

Physical footprint verification is required prior to implementation, as both parts use nonstandard packages (original: 8.30mm x 7.50mm x 5.00mm; substitute: 8.00mm x 8.00mm x 4.20mm).

Frequently Asked Questions (FAQ)

Q: Can the 74404084121 directly replace the SCR74B-121 in all applications?

A: Electrical substitution is valid based on inductance value, tolerance, current rating, and temperature range. Physical footprint compatibility must be verified, as the substitute uses a different nonstandard package size (8.00mm x 8.00mm versus 8.30mm x 7.50mm).

Q: What is the significance of the lower DC resistance in the substitute part?

A: The 74404084121 exhibits 347mOhm DC resistance compared to 680mOhm in the original. This lower resistance reduces power dissipation and heat generation in the inductor, improving overall circuit efficiency.

Q: Does the semi-shielded configuration of the substitute affect performance?

A: The substitute uses semi-shielded construction versus the full shielding of the original. Electromagnetic interference characteristics may differ. Circuit-level EMI testing is recommended if the application requires specific shielding performance.

Q: Are there inventory considerations for this substitution?

A: The SCR74B-121 is obsolete with limited remaining stock (945 pcs). The 74404084121 is in active production with significantly higher availability (2544 pcs), supporting long-term supply chain stability.

Q: What compliance certifications apply to the substitute?

A: The 74404084121 maintains ROHS3 compliance and REACH unaffected status, matching the original part. Additionally, it carries AEC-Q200 automotive qualification, providing enhanced reliability documentation.