PM40-3R9K Equivalent & Substitute Parts

Part Overview

The PM40-3R9K is a 3.9 µH unshielded molded inductor manufactured by Bourns Inc., rated for 330 mA with a maximum DC resistance of 900mOhm. This component operates across a temperature range of -55°C to 125°C in a 1812 (4532 Metric) surface mount package. The part is classified as obsolete, necessitating identification of active equivalent alternatives that maintain electrical and mechanical compatibility for new designs and production continuity.

Substiute Parts

PM40-3R9K

Bourns Inc.In Stock: 786PM40-3R9K Datasheet

Current PartRFQ

CM453232-3R9JL

Bourns Inc.In Stock: 715CM453232-3R9JL Datasheet

DirectRFQ

CM453232-3R9KL

Bourns Inc.In Stock: 4752CM453232-3R9KL Datasheet

DirectRFQ

1812-392J

DelevanIn Stock: 8011812-392J Datasheet

SimilarRFQ

744766039

Würth ElektronikIn Stock: 2795744766039 Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the PM40-3R9K is determined by strict alignment of the following electrical and mechanical parameters:

• Inductance value: 3.9 µH (exact match required)
• Current rating: minimum 330 mA
• DC resistance: 900mOhm maximum
• Package: 1812 (4532 Metric) surface mount
• Shielding configuration: unshielded
• Q factor and self-resonant frequency characteristics

Substitute parts are classified into two categories:

Direct Substitutes maintain all critical electrical parameters and are rated for identical or higher current capacity. These parts are sourced from the same manufacturer (Bourns Inc.) and represent active alternatives with improved compliance status.

Similar Substitutes meet the core electrical specifications but may present variations in secondary parameters such as current rating, operating temperature range, or self-resonant frequency. These parts are from alternative manufacturers and require engineering evaluation for specific application requirements.

Parameter Comparison

Engineering Selection Recommendations

CM453232-3R9KL (Bourns Inc.) is the primary recommended substitute. This part is active, ROHS3 compliant, and maintains identical electrical specifications to the PM40-3R9K with ±10% inductance tolerance. The operating temperature range is reduced to -40°C to 125°C, which is acceptable for most commercial and industrial applications. This part offers the highest inventory availability (4659 pcs) and direct manufacturer continuity.

CM453232-3R9JL (Bourns Inc.) serves as an alternative direct substitute with improved inductance tolerance (±5%) and identical electrical performance. This part is also ROHS3 compliant and active. Selection of this variant is appropriate when tighter inductance tolerance is required by circuit design specifications.

744766039 (Würth Elektronik) is a compliant alternative that meets all core electrical parameters with ROHS3 compliance. The self-resonant frequency is elevated to 120MHz compared to 40MHz in the main part, and the maximum operating temperature is limited to 105°C. This part is suitable for applications where the higher self-resonant frequency does not conflict with circuit requirements and the reduced temperature ceiling is acceptable.

1812-392J (Delevan) provides a non-compliant alternative with higher current rating (472 mA) and identical temperature range (-55°C to 125°C). This part is suitable only for applications where RoHS compliance is not mandated and the elevated current capacity provides design margin.

Frequently Asked Questions (FAQ)

Q: Can CM453232-3R9KL directly replace PM40-3R9K in existing designs?

A: Yes. Both parts share identical inductance (3.9 µH), current rating (330 mA), DC resistance (900mOhm max), and package dimensions (1812/4532 Metric). The primary difference is product status (active vs. obsolete) and RoHS compliance. The operating temperature range is narrower (-40°C to 125°C vs. -55°C to 125°C), which must be verified against application requirements.

Q: What is the difference between CM453232-3R9KL and CM453232-3R9JL?

A: Both parts are electrically equivalent with identical inductance, current rating, and DC resistance. The primary distinction is inductance tolerance: CM453232-3R9KL offers ±10% tolerance, while CM453232-3R9JL provides ±5% tolerance. Selection depends on circuit design tolerance requirements.

Q: Why does 744766039 have a different self-resonant frequency?

A: The Würth Elektronik 744766039 exhibits a self-resonant frequency of 120MHz compared to 40MHz in the PM40-3R9K. This difference results from variations in core material and winding design between manufacturers. Applications operating near or above 40MHz must evaluate whether the elevated self-resonant frequency affects circuit performance.

Q: Is 1812-392J suitable for new production designs?

A: The 1812-392J meets electrical specifications but is RoHS non-compliant. This part is appropriate only for applications where RoHS compliance is not required. For new designs subject to RoHS regulations, CM453232-3R9KL, CM453232-3R9JL, or 744766039 are required.

Q: Are all substitute parts available in the same packaging format?

A: All substitute parts are supplied in 1812 (4532 Metric) surface mount packages. Packaging options vary by supplier: CM453232 variants are supplied in Tape & Reel (TR), 1812-392J is available in Cut Tape (CT) & Digi-Reel, and 744766039 is supplied in Tape & Reel (TR). Verify packaging compatibility with assembly equipment requirements.

Q: What is the minimum current rating required for substitution?

A: The PM40-3R9K is rated for 330 mA. Substitute parts must be rated for a minimum of 330 mA. The 1812-392J (472 mA) and all Bourns alternatives (330 mA) meet this requirement. Higher current ratings provide additional design margin but do not affect substitution eligibility.