KW503J2 Equivalent & Substitute Parts

Part Overview

The KW503J2 is an NTC thermistor bead manufactured by Littelfuse Inc., designed for temperature sensing applications requiring a 50kΩ resistance at 25°C. This component features a B0/50 value of 3892K and operates up to 120°C with a maximum power dissipation of 30mW. The part is classified as obsolete, making identification of suitable substitute components essential for ongoing system support and new design implementations.

Substiute Parts

KW503J2

Littelfuse Inc.In Stock: 952KW503J2 Datasheet

Current PartRFQ

RL0503-27.53K-120-MS

Amphenol ThermometricsIn Stock: 1888RL0503-27.53K-120-MS Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the KW503J2 is determined by the following critical parameters:

• Resistance Value: 50kΩ at 25°C (primary selection criterion)
• Package Type: Bead configuration with free hanging mounting
• Operating Temperature Range: Minimum capability of 120°C
• Regulatory Compliance: ROHS3 compliance required
• Lead Configuration: Compatibility with 1.50" lead wire length or shorter leads acceptable for application redesign

The RL0503-27.53K-120-MS from Amphenol Thermometrics meets these core substitution criteria as an active product with matching resistance value, bead package type, and regulatory compliance.

Parameter Comparison

Engineering Selection Recommendations

The RL0503-27.53K-120-MS is qualified as a direct substitute for the obsolete KW503J2 based on the following factors:

• Both components maintain 50kΩ resistance at 25°C, ensuring functional equivalence in temperature sensing circuits
• The substitute operates across a wider temperature range (-50°C to 150°C), providing enhanced capability beyond the original part's 120°C maximum
• Both components are ROHS3 compliant, meeting current regulatory requirements
• The substitute is an active product with confirmed inventory availability, eliminating obsolescence concerns
• Lead wire length difference (1.13" vs 1.50") requires mechanical verification in the application assembly; shorter leads may necessitate minor PCB layout adjustments

Frequently Asked Questions (FAQ)

Q: Can the RL0503-27.53K-120-MS directly replace the KW503J2 without circuit modifications?

A: The RL0503-27.53K-120-MS provides electrical equivalence at the 50kΩ, 25°C specification point. Physical lead length differs by 0.37" (9.4mm), requiring mechanical fit verification in the assembly. No circuit modifications are necessary if lead length accommodation is addressed.

Q: What is the significance of the resistance tolerance difference (±0.5°C vs ±1%)?

A: The KW503J2 specifies tolerance in temperature units (±0.5°C), while the RL0503-27.53K-120-MS specifies tolerance as a percentage (±1%). Both define acceptable resistance variation at 25°C. Application-specific accuracy requirements determine acceptability.

Q: Why does the substitute have a wider operating temperature range?

A: The RL0503-27.53K-120-MS is rated from -50°C to 150°C, exceeding the KW503J2's 120°C maximum. This extended range reflects the substitute's design capability and does not affect substitution validity for applications operating within the original part's temperature limits.

Q: Are both components suitable for the same mounting applications?

A: Both components feature free hanging bead mounting. The primary consideration is lead wire length compatibility with existing PCB layouts or mechanical assemblies. The shorter lead length of the substitute may require minor positioning adjustments.

Q: What compliance certifications apply to both parts?

A: Both the KW503J2 and RL0503-27.53K-120-MS are ROHS3 compliant. Both carry ECCN EAR99 classification and HTSUS code 8533.40.8070, confirming regulatory alignment for procurement and deployment.