PM40-R68M Equivalent & Substitute Parts

Part Overview

The PM40-R68M is a 680 nH unshielded molded inductor manufactured by Bourns Inc., rated for 450 mA with a maximum DC resistance of 600mOhm. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The part is packaged in 1812 (4532 Metric) surface mount format with an operating temperature range of -55°C to 125°C.

Key Parameters

Parameter	Value
Inductance	680 nH
Inductance Tolerance	±20%
Current Rating	450 mA
DC Resistance (DCR)	600mOhm Max
Package / Case	1812 (4532 Metric)
Mounting Type	Surface Mount
Operating Temperature	-55°C ~ 125°C
Shielding	Unshielded

Substitute Part Grouping Explanation

Substitution for the PM40-R68M is determined by the following critical parameters:

Inductance Value: 680 nH (core electrical requirement)
Package / Case: 1812 (4532 Metric) surface mount (physical compatibility)
Current Rating: Minimum 450 mA (functional requirement)
DC Resistance: Maximum 600mOhm (electrical performance)
Operating Temperature Range: -55°C ~ 125°C (environmental compatibility)
Shielding: Unshielded (electromagnetic characteristic)

Substitute parts are grouped into two categories:

Direct Substitutes (CM453232-R68KL, CM453232-R68ML): These parts meet or exceed all critical parameters with improved specifications. Both are active products from Bourns Inc. with ferrite drum core construction, offering lower DC resistance (400mOhm Max) and higher current ratings (500 mA).

Similar Substitute (1812-681K): This part from API Delevan Inc. matches the inductance value and package format but has different electrical characteristics, including higher DC resistance (1.4Ohm Max) and lower current rating (379 mA).

Parameter Comparison

Parameter	PM40-R68M	CM453232-R68KL	CM453232-R68ML	1812-681K
Manufacturer	Bourns Inc.	Bourns Inc.	Bourns Inc.	API Delevan Inc.
Inductance	680 nH	680 nH	680 nH	680 nH
Inductance Tolerance	±20%	±10%	±20%	±10%
Current Rating (Amps)	450 mA	500 mA	500 mA	379 mA
DC Resistance (DCR)	600mOhm Max	400mOhm Max	400mOhm Max	1.4Ohm Max
Q @ Freq	30 @ 25.2MHz	40 @ 25.2MHz	40 @ 25.2MHz	30 @ 25MHz
Frequency - Self Resonant	160MHz	135MHz	135MHz	150MHz
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
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	RoHS non-compliant
Product Status	Obsolete	Active	Active	Active

Engineering Selection Recommendations

CM453232-R68KL and CM453232-R68ML are the preferred direct substitutes for the PM40-R68M. Both parts are active products from Bourns Inc. with ROHS3 compliance, addressing the obsolescence of the original part. These substitutes provide improved electrical performance with lower DC resistance (400mOhm Max versus 600mOhm Max) and higher current ratings (500 mA versus 450 mA), while maintaining identical inductance and package specifications.

CM453232-R68KL features ±10% inductance tolerance and MSL 1 rating. CM453232-R68ML offers ±20% inductance tolerance matching the original part, with MSL 3 rating (168 Hours). Selection between these two direct substitutes depends on tolerance and moisture sensitivity requirements for your specific application.

1812-681K from API Delevan Inc. is a similar substitute that maintains the same inductance value and package format. However, this part exhibits significantly higher DC resistance (1.4Ohm Max) and lower current rating (379 mA), making it unsuitable for applications requiring the full 450 mA current capacity of the original PM40-R68M. The operating temperature range of -55°C ~ 125°C matches the original part. This option is applicable only when current and resistance specifications can be relaxed.

Frequently Asked Questions (FAQ)

Q: Can CM453232-R68KL and CM453232-R68ML be used interchangeably with PM40-R68M?

A: Yes, both parts are direct substitutes. The primary difference is inductance tolerance (±10% for CM453232-R68KL versus ±20% for CM453232-R68ML) and moisture sensitivity level. CM453232-R68ML matches the original ±20% tolerance specification.

Q: What is the impact of lower DC resistance in the substitute parts?

A: The substitute parts (CM453232-R68KL and CM453232-R68ML) have 400mOhm Max DC resistance compared to 600mOhm Max in the PM40-R68M. Lower DC resistance reduces power dissipation and heat generation in the inductor, which is a performance improvement for most applications.

Q: Is the 1812-681K suitable as a replacement?

A: The 1812-681K maintains the same inductance value and package format but has significantly higher DC resistance (1.4Ohm Max) and lower current rating (379 mA). This part is suitable only for applications where the current requirement is below 379 mA and higher DC resistance is acceptable.

Q: What are the compliance differences between the original and substitute parts?

A: The PM40-R68M is RoHS non-compliant. Both CM453232-R68KL and CM453232-R68ML are ROHS3 compliant, making them suitable for applications requiring RoHS compliance. The 1812-681K remains RoHS non-compliant.

Q: Are there temperature range considerations for substitution?

A: The PM40-R68M operates from -55°C ~ 125°C. The direct substitutes (CM453232-R68KL and CM453232-R68ML) operate from -40°C ~ 125°C, which is a narrower range at the lower temperature limit. For applications requiring operation below -40°C, the original part or 1812-681K (-55°C ~ 125°C) must be used.

Q: What is the difference between MSL 1 and MSL 3 ratings?

A: MSL 1 (Unlimited) indicates no moisture sensitivity restrictions. MSL 3 (168 Hours) indicates the component must be used within 168 hours of package opening under specified humidity conditions. CM453232-R68KL has MSL 1, while CM453232-R68ML has MSL 3.

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