PM40-R33M Equivalent & Substitute Parts

Part Overview

The PM40-R33M is a 330 nH unshielded molded inductor manufactured by Bourns Inc., rated for 450 mA with a maximum DC resistance of 400mOhm. This component operates across -55°C to 125°C and is packaged in the 1812 (4532 Metric) surface mount form factor. The part is currently obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity.

Key Parameters

Parameter	Value
Inductance	330 nH
Tolerance	±20%
Current Rating	450 mA
DC Resistance (Max)	400mOhm
Package / Case	1812 (4532 Metric)
Mounting Type	Surface Mount
Operating Temperature	-55°C ~ 125°C
Shielding	Unshielded
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution eligibility is determined by the following criteria:

Direct Substitutes (Functionally Equivalent): Parts matching inductance value (330 nH), package form factor (1812), surface mount configuration, and unshielded design. Current rating and DC resistance must meet or exceed the original specification to ensure circuit performance.

Similar Substitutes (Compatible with Design Review): Parts with the same inductance and package but differing in core material, tolerance, or DC resistance characteristics. These require verification against circuit requirements.

Non-Equivalent Parts (Listed for Reference): Parts with significantly different inductance values or package specifications that do not qualify as direct substitutes.

Parameter Comparison

Part Number	Manufacturer	Inductance	Tolerance	Current Rating (mA)	DCR Max (mOhm)	Core Type	Package	Operating Temp	Product Status	RoHS Status
PM40-R33M	Bourns Inc.	330 nH	±20%	450	400	Non-Magnetic	1812 (4532)	-55°C ~ 125°C	Obsolete	Non-compliant
CM453232-R33ML	Bourns Inc.	330 nH	±20%	605	280	Ferrite	1812 (4532)	-40°C ~ 125°C	Active	ROHS3 Compliant
CM453232-R33KL	Bourns Inc.	330 nH	±10%	605	280	Ferrite	1812 (4532)	-40°C ~ 125°C	Active	ROHS3 Compliant
1812-331K	API Delevan Inc.	330 nH	±10%	604	550	Iron	1812 (4532)	-55°C ~ 125°C	Active	Non-compliant
SDR0403-390KL	Bourns Inc.	39 µH	±10%	590	590	Ferrite	Nonstandard	-40°C ~ 125°C	Active	ROHS3 Compliant

Engineering Selection Recommendations

Recommended Direct Substitutes:

CM453232-R33ML and CM453232-R33KL are the primary alternatives for PM40-R33M replacement. Both parts maintain the 330 nH inductance and 1812 package specification. The CM453232-R33ML offers ±20% tolerance matching the original part, while CM453232-R33KL provides tighter ±10% tolerance. Both deliver superior current ratings (605 mA vs. 450 mA) and lower DC resistance (280mOhm vs. 400mOhm), improving circuit efficiency. Both are ROHS3 compliant and in active production status. The primary design consideration is the reduced lower operating temperature limit (-40°C vs. -55°C).

Alternative Substitute:

1812-331K from API Delevan Inc. maintains 330 nH inductance, ±10% tolerance, and 1812 package compatibility. Current rating (604 mA) and operating temperature range (-55°C ~ 125°C) align closely with the original specification. DC resistance (550mOhm) is higher than the original, which may impact circuit performance in current-sensitive applications. This part is not RoHS compliant.

Non-Recommended:

SDR0403-390KL has a significantly different inductance value (39 µH) and nonstandard package, making it unsuitable for direct substitution despite active status and RoHS compliance.

Frequently Asked Questions (FAQ)

Q: Can CM453232-R33ML directly replace PM40-R33M without circuit modification?

A: Yes, for most applications. Both parts share 330 nH inductance, ±20% tolerance, and 1812 package. The substitute offers improved electrical performance (higher current rating, lower DC resistance). The reduced lower operating temperature limit (-40°C vs. -55°C) must be verified against your application requirements.

Q: What is the difference between CM453232-R33ML and CM453232-R33KL?

A: Both are functionally equivalent with identical inductance, current rating, and DC resistance. CM453232-R33KL provides tighter tolerance (±10% vs. ±20%), beneficial for precision-critical circuits. CM453232-R33ML offers unlimited moisture sensitivity (MSL 1), while CM453232-R33KL requires 168-hour storage control (MSL 3).

Q: Why is SDR0403-390KL listed if it cannot substitute?

A: SDR0403-390KL is included for reference as it appears in the original part's substitute list. However, the 39 µH inductance and nonstandard package make it incompatible with PM40-R33M applications requiring 330 nH.

Q: Is the 1812-331K from API Delevan a viable alternative?

A: The 1812-331K maintains package and inductance compatibility with acceptable current rating and temperature range. However, higher DC resistance (550mOhm vs. 400mOhm) may increase power dissipation. Non-RoHS compliance may conflict with regulatory requirements. Evaluate against specific circuit performance criteria.

Q: What are the key electrical differences between the original and recommended substitutes?

A: The primary differences are core material (non-magnetic to ferrite), DC resistance (400mOhm to 280mOhm), and current rating (450 mA to 605 mA). These changes improve efficiency and thermal performance. Inductance tolerance remains equivalent or tighter in substitutes.

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