PM40-R12M Equivalent & Substitute Parts

Part Overview

The PM40-R12M is a 120 nH unshielded molded inductor manufactured by Bourns Inc., rated for 450 mA with a maximum DC resistance of 220mOhm in a 1812 (4532 Metric) surface mount package. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Key Parameters

Parameter	Value
Inductance	120 nH
Current Rating	450 mA
DC Resistance (DCR)	220mOhm Max
Package / Case	1812 (4532 Metric)
Mounting Type	Surface Mount
Operating Temperature	-55°C ~ 125°C
Shielding	Unshielded
Frequency - Self Resonant	500 MHz

Substitute Part Grouping Explanation

Substitution for the PM40-R12M is determined by the following critical parameters:

Inductance Value: 120 nH (exact match required)
Package / Case: 1812 (4532 Metric) surface mount (physical and electrical compatibility)
Current Rating: Minimum 450 mA (substitute must meet or exceed)
DC Resistance: Maximum 220mOhm (electrical performance requirement)
Operating Temperature Range: -55°C ~ 125°C (environmental compatibility)
Shielding: Unshielded (electromagnetic characteristic)

The substitute parts listed below meet these core electrical and mechanical parameters within acceptable tolerances for direct circuit replacement.

Parameter Comparison

Parameter	PM40-R12M	CM453232-R12KL	CM453232-R12ML	1812-121K
Manufacturer	Bourns Inc.	Bourns Inc.	Bourns Inc.	API Delevan Inc.
Inductance	120 nH	120 nH	120 nH	120 nH
Tolerance	±20%	±10%	±20%	±10%
Current Rating (Amps)	450 mA	770 mA	770 mA	818 mA
DC Resistance (DCR)	220mOhm Max	200mOhm Max	200mOhm Max	300mOhm Max
Q @ Freq	30 @ 25.2MHz	35 @ 25.2MHz	35 @ 25.2MHz	30 @ 25MHz
Frequency - Self Resonant	500 MHz	280 MHz	280 MHz	600 MHz
Operating Temperature	-55°C ~ 125°C	-40°C ~ 125°C	-40°C ~ 125°C	-55°C ~ 125°C
Package / Case	1812 (4532 Metric)	1812 (4532 Metric)	1812 (4532 Metric)	1812 (4532 Metric)
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Shielding	Unshielded	Unshielded	Unshielded	Unshielded
Product Status	Obsolete	Active	Active	Active
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	RoHS non-compliant

Engineering Selection Recommendations

Direct Substitutes (Bourns CM453232 Series)

CM453232-R12KL and CM453232-R12ML are active production parts from Bourns Inc. with superior electrical characteristics compared to the obsolete PM40-R12M. Both parts exceed the current rating requirement (770 mA vs. 450 mA), feature lower DC resistance (200mOhm vs. 220mOhm), and achieve higher Q factor (35 vs. 30 @ 25.2MHz). Both are ROHS3 compliant, addressing regulatory requirements. The primary trade-off is a reduced self-resonant frequency (280 MHz vs. 500 MHz) and narrower operating temperature range (-40°C to 125°C vs. -55°C to 125°C). CM453232-R12KL offers tighter inductance tolerance (±10% vs. ±20%), while CM453232-R12ML matches the original tolerance specification.

Alternative Substitute (API Delevan 1812-121K)

The 1812-121K from API Delevan Inc. is an active production part with the highest current rating (818 mA) and maintains the full operating temperature range (-55°C to 125°C) of the original part. However, it exhibits higher DC resistance (300mOhm vs. 220mOhm) and lower Q factor (30 @ 25MHz). This part is RoHS non-compliant and should be selected only when the extended low-temperature capability is required and regulatory compliance is not a constraint.

Frequently Asked Questions (FAQ)

Q: Can CM453232-R12KL or CM453232-R12ML be used as direct replacements for PM40-R12M?

A: Yes. Both parts share the same 120 nH inductance value, 1812 (4532 Metric) package, and unshielded configuration. Both exceed the current rating and meet or improve upon the DC resistance specification. The primary consideration is the reduced self-resonant frequency (280 MHz vs. 500 MHz) and narrower operating temperature range (-40°C to 125°C vs. -55°C to 125°C). Verify these parameters against your circuit requirements before selection.

Q: What is the difference between CM453232-R12KL and CM453232-R12ML?

A: Both parts are electrically identical with the same current rating (770 mA), DC resistance (200mOhm Max), and Q factor (35 @ 25.2MHz). The difference is inductance tolerance: CM453232-R12KL specifies ±10% tolerance, while CM453232-R12ML specifies ±20% tolerance, matching the original PM40-R12M specification.

Q: Why does the 1812-121K have higher DC resistance than the substitute Bourns parts?

A: The 1812-121K uses an iron core material, while the CM453232 series uses ferrite core material. Core material selection affects DC resistance characteristics. The higher DC resistance of the 1812-121K may impact power dissipation in high-current applications.

Q: Are there temperature range limitations with the Bourns CM453232 substitutes?

A: Yes. The CM453232-R12KL and CM453232-R12ML operate from -40°C to 125°C, compared to the original PM40-R12M range of -55°C to 125°C. If your application requires operation below -40°C, the 1812-121K maintains the full -55°C to 125°C range.

Q: What is the impact of the reduced self-resonant frequency in the Bourns substitutes?

A: The CM453232 series has a self-resonant frequency of 280 MHz compared to 500 MHz for the PM40-R12M. This affects high-frequency performance characteristics. For circuits operating near or above 280 MHz, evaluate the impact on impedance and filtering behavior.

Q: Are the substitute parts RoHS compliant?

A: CM453232-R12KL and CM453232-R12ML are ROHS3 compliant. The 1812-121K is RoHS non-compliant. Select based on your regulatory requirements.

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