Equivalent & Substitute Parts for 104LG2K

Part Overview

The 104LG2K is an NTC thermistor manufactured by Littelfuse Inc., featuring a nominal resistance of 100kΩ at 25°C with a B-value of 3920K at the 25°C/85°C reference point. This component is packaged in a DO-204AH (DO-35) axial configuration with 1.00" lead wire length and supports operating temperatures up to 300°C. The product is currently classified as obsolete, necessitating identification of functionally equivalent alternatives for ongoing applications and new designs.

Substiute Parts

104LG2K

Littelfuse Inc.In Stock: 835104LG2K Datasheet

Current PartRFQ

135-104LAG-J01

Honeywell Sensing and Productivity SolutionsIn Stock: 1362135-104LAG-J01 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the 104LG2K is determined by the following critical parameters:

• Resistance Value: 100kΩ nominal at 25°C with ±10% tolerance
• B-Value Specification: Temperature coefficient in the 3920K–3974K range at the 25°C/85°C reference point
• Package Configuration: DO-204AH (DO-35) axial through-hole format
• Operating Temperature: Maximum rating of 300°C or higher
• Lead Wire Length: Compatibility within standard axial lead dimensions

The substitute part 135-104LAG-J01 meets all these criteria, providing functional equivalence for thermal sensing applications requiring these specifications.

Parameter Comparison

Engineering Selection Recommendations

The 135-104LAG-J01 is the designated manufacturer-recommended substitute for the obsolete 104LG2K. Selection of this alternative is supported by:

• Active Product Status: The Honeywell part is in active production, ensuring long-term availability and supply chain continuity.
• Compliance Certifications: RoHS compliance and REACH unaffected status align with current regulatory requirements.
• Thermal Performance: B-value of 3974K at 25°C/85°C is within acceptable tolerance of the original 3920K specification, maintaining thermal response characteristics.
• Mechanical Compatibility: Identical package configuration (DO-204AH, DO-35, axial) and through-hole mounting ensure direct circuit board integration.
• Temperature Range: Extended lower temperature limit (-60°C) provides broader operational capability while maintaining the 300°C upper limit.

Lead wire length variation (1.13" vs. 1.00") is a minor mechanical difference that does not affect electrical performance and is accommodated in standard through-hole PCB layouts.

Frequently Asked Questions (FAQ)

Q: Can the 135-104LAG-J01 directly replace the 104LG2K in existing designs?

A: Yes. Both components share identical resistance values (100kΩ), tolerance specifications (±10%), package configuration (DO-204AH, DO-35, axial), and maximum operating temperature (300°C). The B-value difference (3974K vs. 3920K) is within acceptable thermal sensing tolerances for most applications.

Q: What is the significance of the B-value difference between these parts?

A: The B-value determines the thermistor's temperature coefficient. The 54K difference (3974K vs. 3920K) represents approximately 1.4% variation in thermal response. This difference is negligible for general temperature sensing applications and falls within typical circuit design margins.

Q: Does the lead wire length difference affect circuit compatibility?

A: The 0.13" (3.2mm) difference in lead wire length is a minor mechanical variation. Standard through-hole PCB designs accommodate this variation without modification. Lead length does not affect electrical performance.

Q: Is the 135-104LAG-J01 RoHS compliant?

A: Yes. The Honeywell 135-104LAG-J01 is RoHS compliant, meeting current environmental and regulatory standards. The original 104LG2K RoHS status was not specified.

Q: What is the MSL (Moisture Sensitivity Level) of the substitute part?

A: The 135-104LAG-J01 has an MSL rating of 1 (Unlimited), indicating no moisture sensitivity restrictions for storage or handling.

Q: Are there any electrical performance differences that would require circuit redesign?

A: No. Both components are functionally equivalent for thermal sensing applications. Identical resistance values, tolerance specifications, and package configurations ensure drop-in compatibility without circuit modifications.