RB503K0J NTC Thermistor 50kΩ 0603 Equivalent & Substitute Parts

Part Overview

The RB503K0J is an NTC thermistor manufactured by Littelfuse Inc., designed for temperature sensing applications requiring a 50kΩ resistance at 25°C in a compact 0603 (1608 Metric) surface mount package. This component operates across a temperature range of -40°C to 125°C with a maximum power dissipation of 150 mW. The part is classified as obsolete, necessitating identification of functionally equivalent alternatives for ongoing design support and procurement.

Substiute Parts

RB503K0J

Littelfuse Inc.In Stock: 820RB503K0J Datasheet

Current PartRFQ

NTHS0603N01N5002FE

Vishay DaleIn Stock: 30251NTHS0603N01N5002FE Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the RB503K0J is determined by strict adherence to the following electrical and mechanical parameters:

Critical Matching Parameters:

• Resistance value: 50kΩ at 25°C
• Package / Case: 0603 (1608 Metric) surface mount
• Operating temperature range: -40°C to 125°C minimum
• Mounting type: Surface mount

Acceptable Variation Parameters:

• Resistance tolerance: May be tighter (lower tolerance value) than the original ±5%
• Power dissipation: Must meet or exceed 125 mW minimum
• B-value characteristics: Must support the operating temperature range

The NTHS0603N01N5002FE from Vishay Dale meets all critical matching parameters and qualifies as a direct substitute.

Parameter Comparison

Engineering Selection Recommendations

The NTHS0603N01N5002FE is electrically and mechanically compatible with the RB503K0J for direct substitution in existing designs. Both components maintain identical package geometry, operating temperature range, and moisture sensitivity classification. The substitute part offers improved resistance tolerance (±1% versus ±5%), which provides tighter performance specifications. The B25/85 value differential of 26K (3974K versus 4000K) represents a 0.65% variation within acceptable engineering margins for NTC thermistor applications. Both parts maintain ROHS3 compliance and REACH unaffected status. The maximum power dissipation of the substitute (125 mW) remains adequate for applications designed around the original 150 mW specification, provided thermal design margins are verified for the specific application circuit.

Frequently Asked Questions (FAQ)

Q: Can the NTHS0603N01N5002FE replace the RB503K0J in existing PCB designs without layout modifications?

A: Yes. Both components use identical 0603 (1608 Metric) surface mount packaging with matching footprints and lead configurations. No PCB layout changes are required.

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

A: The B25/85 value characterizes the thermistor's temperature-resistance relationship. The 26K difference (3974K versus 4000K) represents a 0.65% variation. This minor difference affects the resistance-temperature curve slope and is acceptable for most temperature sensing applications within the -40°C to 125°C operating range.

Q: Does the lower power dissipation rating of the substitute part affect circuit performance?

A: The NTHS0603N01N5002FE is rated for 125 mW maximum power dissipation compared to the original 150 mW. Applications must ensure actual power dissipation remains below 125 mW. For designs operating near the original 150 mW limit, thermal analysis is required to confirm the substitute part operates within safe margins.

Q: Are there compliance or regulatory differences between these parts?

A: Both parts are ROHS3 compliant, REACH unaffected, and classified under identical ECCN and HTSUS codes. No compliance differences exist for regulatory or environmental standards.

Q: Why is the substitute part listed as "Not For New Designs"?

A: This product status designation indicates the manufacturer is not recommending this part for new design implementations. However, it remains suitable for replacement and maintenance of existing designs using the original RB503K0J.