PM40-R39M Equivalent & Substitute Parts Reference

Part Overview

The PM40-R39M is a 390 nH unshielded molded inductor manufactured by Bourns Inc., rated for 450 mA with a maximum DC resistance of 450mOhm. This component is classified as obsolete, making equivalent substitutes necessary for ongoing production and maintenance applications. The part is packaged in 1812 (4532 Metric) surface mount format with operating temperature range of -55°C to 125°C.

Substiute Parts

PM40-R39M

Bourns Inc.In Stock: 1175PM40-R39M Datasheet

Current PartRFQ

CM453232-R39KL

Bourns Inc.In Stock: 1033CM453232-R39KL Datasheet

DirectRFQ

CM453232-R39ML

Bourns Inc.In Stock: 2375CM453232-R39ML Datasheet

DirectRFQ

1812-391K

API Delevan Inc.In Stock: 11841812-391K Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the PM40-R39M is determined by the following critical parameters:

• Inductance Value: Must be 390 nH (exact match required)
• Package / Case: Must be 1812 (4532 Metric) surface mount
• Current Rating: Must meet or exceed 450 mA minimum requirement
• DC Resistance: Must not exceed 450mOhm maximum specification
• Shielding Configuration: Must be unshielded
• Operating Temperature Range: Must support -55°C to 125°C minimum

The substitute parts listed below satisfy these core electrical and mechanical parameters, enabling direct replacement in circuit applications where the PM40-R39M is specified.

Parameter Comparison

Engineering Selection Recommendations

CM453232-R39KL and CM453232-R39ML (Direct Substitutes)

Both CM45 series inductors from Bourns Inc. are active products with ROHS3 compliance. These parts exceed the current rating requirement (575 mA vs. 450 mA) and provide superior DC resistance performance (300mOhm vs. 450mOhm maximum). The CM453232-R39ML variant matches the ±20% tolerance of the original PM40-R39M, while CM453232-R39KL offers tighter ±10% tolerance. Both support the 1812 package footprint with identical mechanical dimensions. The reduced operating temperature minimum (-40°C vs. -55°C) must be evaluated against application requirements. These parts are preferred for new designs and production transitions due to active status and regulatory compliance.

1812-391K (Similar Substitute)

The 1812-391K from API Delevan Inc. maintains the full -55°C to 125°C operating temperature range of the original part. Current rating (535 mA) and package format are compatible. However, DC resistance is elevated at 700mOhm maximum, exceeding the PM40-R39M specification by 250mOhm. This part is RoHS non-compliant, matching the original part's regulatory status. Selection of this substitute is appropriate only when the elevated DC resistance is acceptable for the circuit application and when RoHS compliance is not required.

Frequently Asked Questions (FAQ)

Q: Can CM453232-R39KL and CM453232-R39ML be used interchangeably with PM40-R39M?

A: Both CM45 series parts satisfy the core electrical parameters: 390 nH inductance, 1812 package, unshielded configuration, and current ratings exceeding 450 mA. The primary consideration is the reduced minimum operating temperature (-40°C vs. -55°C). If the application operates within -40°C to 125°C, these parts are direct substitutes. The CM453232-R39ML maintains ±20% tolerance matching the original; CM453232-R39KL provides ±10% tolerance for tighter inductance control.

Q: What is the impact of lower DC resistance in the CM45 series substitutes?

A: The CM45 series offers 300mOhm maximum DC resistance compared to 450mOhm in the PM40-R39M. Lower DC resistance reduces power dissipation and heat generation in the inductor, improving circuit efficiency. This is a beneficial characteristic and does not create compatibility issues.

Q: Is the 1812-391K suitable as a substitute?

A: The 1812-391K meets the inductance value, package format, current rating, and full temperature range requirements. However, its 700mOhm maximum DC resistance exceeds the PM40-R39M specification by 250mOhm. This part is suitable only if circuit design tolerates the higher DC resistance and associated power loss. RoHS non-compliance matches the original part's status.

Q: What are the mechanical compatibility considerations?

A: All substitute parts use the 1812 (4532 Metric) surface mount package with identical footprint dimensions (0.177" L x 0.126" W / 4.50mm x 3.20mm). Height differences are minimal: CM45 series parts measure 0.134" (3.40mm) maximum seated height versus 0.126" (3.20mm) for the PM40-R39M. These height variations are within standard PCB assembly tolerances and do not affect placement or soldering.

Q: Should RoHS compliance status influence substitute selection?

A: The PM40-R39M is RoHS non-compliant. If the application or end-market requires RoHS compliance, the CM453232-R39KL and CM453232-R39ML (both ROHS3 compliant) are the appropriate choices. The 1812-391K maintains RoHS non-compliant status, matching the original part's regulatory profile.