MICROSMD550LR-2 Equivalent & Substitute Parts

Part Overview

The MICROSMD550LR-2 is a Polymeric PTC Resettable Fuse manufactured by Littelfuse Inc., rated for 5V at 5.5A hold current in a 1210 (3225 Metric) surface mount package. This component is classified as Obsolete, necessitating identification of active equivalent parts for ongoing design requirements and procurement needs. Substitute parts must maintain electrical compatibility within the specified voltage, current, and thermal parameters while accommodating the surface mount 1210 package format.

Substiute Parts

MICROSMD550LR-2

Littelfuse Inc.In Stock: 1013MICROSMD550LR-2 Datasheet

Current PartRFQ

1210L550SLWR

Littelfuse Inc.In Stock: 27511210L550SLWR Datasheet

DirectRFQ

PTSLR12106V550

Eaton - Electronics DivisionIn Stock: 4801PTSLR12106V550 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the MICROSMD550LR-2 are identified based on the following electrical and mechanical compatibility criteria:

Primary Substitution Parameters:

• Voltage rating equal to or greater than 5V
• Current hold (Ih) rating of 5.5A
• Current trip (It) rating of 11A
• Surface mount 1210 (3225 Metric) package format
• Polymeric PTC resettable fuse technology
• RoHS3 compliance

The identified substitutes maintain the critical hold current and trip current specifications while accommodating voltage ratings of 6V, which provides backward compatibility for 5V circuit applications. Both substitute parts are classified as Active products with current manufacturing availability.

Parameter Comparison

Engineering Selection Recommendations

1210L550SLWR (Littelfuse Inc., POLY-FUSE® LoRho Series)

This part is classified as Active with current manufacturing availability. It maintains identical hold and trip current specifications (5.5A / 11A) and operates within an expanded temperature range (-40°C ~ 85°C). The 6V voltage rating accommodates 5V circuit applications. Certifications include cURus and TUV approval. Initial resistance is lower (1 mOhm minimum) compared to the original part, and post-trip resistance is higher (11 mOhms maximum). Moisture sensitivity is rated 1 (Unlimited), providing superior environmental stability compared to the original 2A rating.

PTSLR12106V550 (Eaton - Electronics Division, PTSLR1210 Series)

This part is classified as Active with current manufacturing availability. It maintains identical hold and trip current specifications (5.5A / 11A) and operates within an expanded temperature range (-40°C ~ 85°C). The 6V voltage rating accommodates 5V circuit applications. Certifications include cURus and TUV approval. Time to trip is specified at 5 seconds, compared to 2 seconds for the original part. Initial resistance is lower (1 mOhm minimum) and post-trip resistance is 10 mOhms maximum. Physical dimensions differ slightly (0.135" L x 0.110" W versus 0.127" L x 0.102" W for the original).

Frequently Asked Questions (FAQ)

Q: Can 1210L550SLWR or PTSLR12106V550 be used in place of MICROSMD550LR-2?

A: Both parts are electrically compatible for 5V circuit applications. They maintain the critical 5.5A hold current and 11A trip current specifications. The 6V voltage rating of both substitutes provides adequate margin for 5V operation. Physical package format (1210 Concave) is identical, enabling direct PCB footprint compatibility.

Q: What is the significance of the voltage rating difference (5V vs. 6V)?

A: The substitute parts are rated for 6V maximum voltage, which is higher than the original 5V rating. In a 5V circuit application, this provides additional voltage margin and does not create compatibility issues. The hold current and trip current thresholds remain the same across all three parts.

Q: How do the time-to-trip specifications differ?

A: MICROSMD550LR-2 and 1210L550SLWR both specify 2-second trip time. PTSLR12106V550 specifies 5-second trip time. This difference affects the response speed during overcurrent events. Circuit design requirements should determine which trip time is appropriate for the application.

Q: Are there differences in initial and post-trip resistance?

A: Yes. MICROSMD550LR-2 specifies 2 mOhms minimum initial resistance and 6.5 mOhms maximum post-trip resistance. Both substitutes specify 1 mOhm minimum initial resistance, with post-trip resistance of 11 mOhms (1210L550SLWR) and 10 mOhms (PTSLR12106V550). These differences affect power dissipation characteristics and should be evaluated against circuit thermal requirements.

Q: What are the moisture sensitivity implications?

A: MICROSMD550LR-2 is rated MSL 2A (4 Weeks). 1210L550SLWR is rated MSL 1 (Unlimited), providing superior moisture resistance. PTSLR12106V550 is rated MSL 2A (4 Weeks), matching the original part. MSL rating affects storage and handling requirements prior to assembly.

Q: Do the operating temperature ranges differ?

A: MICROSMD550LR-2 operates from -40°C to 80°C. Both substitutes operate from -40°C to 85°C, providing a 5-degree expansion of the upper temperature limit. This expanded range may be beneficial in thermal-constrained applications.

Q: Are both substitutes certified?

A: Yes. Both 1210L550SLWR and PTSLR12106V550 carry cURus and TUV certifications. MICROSMD550LR-2 does not list approval agencies. All three parts are RoHS3 compliant.