PM125S-331M-RC Equivalent & Substitute Parts

Part Overview

The PM125S-331M-RC is a 330 µH shielded drum core, wirewound inductor manufactured by Bourns Inc., rated for 570 mA continuous current with a maximum DC resistance of 800mOhm. This component is classified as obsolete, making identification of suitable substitute parts essential for ongoing design support and production continuity. The part operates across the industrial temperature range of -40°C to 125°C and is fully RoHS3 compliant.

Substiute Parts

PM125S-331M-RC

Bourns Inc.In Stock: 1226PM125S-331M-RC Datasheet

Current PartRFQ

SRR1205-331KL

Bourns Inc.In Stock: 752SRR1205-331KL Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the PM125S-331M-RC is based on the following critical parameters:

• Inductance Value: 330 µH (primary electrical requirement)
• Core Type & Shielding: Ferrite, shielded drum core (electromagnetic performance)
• Current Rating: Minimum 540 mA acceptable for applications rated at 570 mA
• Saturation Current: Minimum 880 mA provides adequate margin
• DC Resistance: Up to 1.34 Ohm acceptable depending on circuit thermal budget
• Mounting & Package: Surface mount, nonstandard package footprint
• Temperature Range: -40°C to 125°C (matching operational envelope)
• Compliance: RoHS3 and REACH requirements

The SRR1205-331KL meets these substitution criteria while offering improved inductance tolerance (±10% vs ±20%) and higher saturation current (880 mA vs 780 mA).

Parameter Comparison

Engineering Selection Recommendations

The SRR1205-331KL is the designated substitute for the obsolete PM125S-331M-RC based on electrical equivalence and compliance alignment. Both components are RoHS3 compliant and REACH unaffected, ensuring regulatory continuity.

Selection of the SRR1205-331KL requires verification of the following circuit-specific factors:

• Current Margin: The substitute is rated 30 mA below the original part. Confirm that circuit operating current does not exceed 540 mA continuous.
• Thermal Performance: The substitute exhibits 1.34 Ohm DCR versus 800 mOhm in the original. Calculate power dissipation (I²R) to ensure thermal design remains within acceptable limits.
• Frequency Response: The substitute has a self-resonant frequency of 2 MHz compared to 4 MHz in the original. Verify that circuit operating frequencies remain below the substitute's SRF to avoid impedance anomalies.
• Physical Footprint: Dimensional differences (12.70mm x 12.70mm vs 12.60mm x 11.60mm) require PCB layout confirmation to ensure mechanical fit and clearance.

The active production status of the SRR1205-331KL ensures long-term availability and supply chain stability compared to the obsolete PM125S-331M-RC.

Frequently Asked Questions (FAQ)

Q: Can the SRR1205-331KL directly replace the PM125S-331M-RC without circuit modification?

A: Direct replacement is possible if circuit operating current remains below 540 mA and thermal dissipation from the higher DCR (1.34 Ohm vs 800 mOhm) is acceptable. PCB layout must accommodate the slightly larger footprint (12.70mm x 12.70mm).

Q: What is the impact of the lower self-resonant frequency (2 MHz vs 4 MHz) on circuit performance?

A: The substitute's lower SRF may affect high-frequency performance. If the circuit operates near or above 2 MHz, impedance characteristics will deviate from the original part. Confirm that circuit operating frequencies remain well below 2 MHz.

Q: Are there packaging differences between these parts?

A: The PM125S-331M-RC uses nonstandard packaging, while the SRR1205-331KL is supplied in Tape & Reel (TR) format. Both are surface mount components with compatible mounting processes.

Q: How does the inductance tolerance difference affect circuit design?

A: The SRR1205-331KL offers ±10% tolerance versus ±20% for the original part. This tighter tolerance may improve circuit performance consistency but does not prevent substitution in applications designed for ±20% tolerance.

Q: Is thermal management a concern when substituting?

A: Yes. The substitute's DCR of 1.34 Ohm is 67% higher than the original 800 mOhm. At 540 mA, power dissipation increases from 233 mW to 391 mW. Verify that PCB thermal design accommodates this additional heat generation.