MICROSMD200LR-2 Equivalent & Substitute Parts

Part Overview

The MICROSMD200LR-2 is a Polymeric PTC Resettable Fuse manufactured by Littelfuse Inc., rated for 6V at 2A hold current in a 1210 (3225 Metric) surface mount package. This component is classified as Obsolete, making identification of functionally equivalent alternatives essential for ongoing design support and production continuity. Substitute parts must maintain electrical compatibility while accommodating available package options and current product status.

Key Parameters

Parameter	MICROSMD200LR-2
Manufacturer	Littelfuse Inc.
Voltage - Max	6V
Current - Hold (Ih) (Max)	2 A
Current - Trip (It)	5 A
Current - Max	50 A
Time to Trip	4 s
Resistance - Initial (Ri) (Min)	6 mOhms
Type	Polymeric
Mounting Type	Surface Mount
Package / Case	1210 (3225 Metric), Concave
Product Status	Obsolete
RoHS Status	ROHS3 Compliant
Approval Agency	CSA, UL

Substitute Part Grouping Explanation

Substitution of the MICROSMD200LR-2 is determined by the following electrical and mechanical criteria:

Primary Substitution Criteria:

Voltage rating: 6V maximum (all substitutes must equal or exceed this rating)
Current hold (Ih): Substitutes must support the application's required hold current
Package compatibility: Surface mount polymeric PTC fuses with concave geometry
Compliance: RoHS3 compliance and recognized approval agencies (cURus, TUV, CSA, UL)

Substitution Logic: Substitute parts are grouped by current hold rating, as this parameter directly determines circuit protection characteristics. Parts with lower Ih ratings (0.35A to 1.75A) provide protection for lower-current applications, while parts with higher Ih ratings accommodate higher-current circuits. All substitutes maintain 6V maximum voltage rating and polymeric construction. Package sizes range from 0402 (1005 Metric) to 0805 (2012 Metric), allowing flexibility in PCB layout constraints while maintaining electrical equivalence within their respective current classes.

Parameter Comparison

Part Number	Manufacturer	Voltage - Max	Current - Hold (Ih) (Max)	Current - Trip (It)	Resistance - Initial (Ri) (Min)	Package / Case	Product Status	Approval Agency
MICROSMD200LR-2	Littelfuse Inc.	6V	2 A	5 A	6 mOhms	1210 (3225 Metric)	Obsolete	CSA, UL
0402L035SLKR	Littelfuse	6V	350 mA	700 mA	50 mOhms	0402 (1005 Metric)	Active	cURus, TUV
0402L050SLKR	Littelfuse	6V	500 mA	1 A	40 mOhms	0402 (1005 Metric)	Active	cURus, TUV
0603L050SLYR	Littelfuse Inc.	6V	500 mA	1 A	70 mOhms	0603 (1608 Metric)	Active	cURus, TUV
0603L075SLYR	Littelfuse Inc.	6V	750 mA	1.5 A	20 mOhms	0603 (1608 Metric)	Active	cURus, TUV
0603L100SLYR	Littelfuse Inc.	6V	1 A	1.8 A	40 mOhms	0603 (1608 Metric)	Active	cURus, TUV
0603L150SLYR	Littelfuse Inc.	6V	1.5 A	3 A	7 mOhms	0603 (1608 Metric)	Active	cURus, TUV
0603L175SLYR	Littelfuse Inc.	6V	1.75 A	4.6 A	5 mOhms	0603 (1608 Metric)	Active	cURus, TUV
0805L110SLYR	Littelfuse Inc.	6V	1.1 A	1.8 A	30 mOhms	0805 (2012 Metric)	Active	cURus, TUV
0805L150SLYR	Littelfuse Inc.	6V	1.5 A	3 A	15 mOhms	0805 (2012 Metric)	Active	cURus, TUV
0805L175SLYR	Littelfuse Inc.	6V	1.75 A	4.6 A	5 mOhms	0805 (2012 Metric)	Active	cURus, TUV

Engineering Selection Recommendations

All listed substitute parts are Active product status components from Littelfuse, ensuring long-term availability and manufacturing support. The MICROSMD200LR-2 is Obsolete; therefore, migration to an Active equivalent is necessary for new designs and production continuity.

Compliance Considerations:

Original part: CSA, UL approval
Substitute parts: cURus, TUV approval with ROHS3 compliance

All substitutes maintain ROHS3 compliance and carry recognized international certifications suitable for industrial and consumer applications.

Current Rating Selection: For direct functional replacement of the 2A hold current specification, the 0603L175SLYR or 0805L175SLYR (1.75A Ih) provide the closest electrical match. The 0603L150SLYR and 0805L150SLYR (1.5A Ih) offer slightly lower hold current ratings. Lower-current alternatives (0.35A to 1.1A) are suitable only for applications requiring reduced protection thresholds.

Package Considerations: The original 1210 package is not available in the substitute list. Selection between 0603 and 0805 packages depends on PCB layout constraints and thermal management requirements. The 0603 package offers space efficiency, while the 0805 package provides improved thermal characteristics.

Frequently Asked Questions (FAQ)

Q: Can I use a lower current-rated substitute (e.g., 0603L100SLYR at 1A) in place of the MICROSMD200LR-2 (2A)?

A: No. The hold current (Ih) rating determines the maximum continuous current the fuse allows before tripping. Using a lower-rated substitute will cause nuisance tripping at normal operating currents. Select a substitute with Ih rating equal to or greater than the original 2A specification.

Q: What is the difference between Current - Hold (Ih) and Current - Trip (It)?

A: Current - Hold (Ih) is the maximum continuous current the fuse permits indefinitely without tripping. Current - Trip (It) is the threshold at which the fuse begins thermal response. For the MICROSMD200LR-2, Ih is 2A and It is 5A. Substitute selection must preserve the Ih rating for the application.

Q: Are the 0603 and 0805 packages electrically equivalent to the original 1210 package?

A: Yes, within their respective current ratings. Package size differences are mechanical only. The 0603 (1608 Metric) and 0805 (2012 Metric) packages are smaller than the original 1210 (3225 Metric), allowing PCB redesign flexibility. Electrical performance is determined by voltage, current, and resistance specifications, not package size.

Q: Why do substitute parts have different approval agencies (cURus, TUV) compared to the original (CSA, UL)?

A: Littelfuse manufactures these parts to meet multiple international standards. The original part carries CSA and UL approvals; substitutes carry cURus and TUV approvals. Both certification sets meet equivalent safety and performance standards for polymeric PTC fuses in 6V applications.

Q: Can I use 0603L175SLYR as a direct replacement for MICROSMD200LR-2?

A: The 0603L175SLYR (1.75A Ih) is electrically compatible with the MICROSMD200LR-2 (2A Ih) for most applications, as the hold current difference is minimal. However, PCB layout must accommodate the smaller 0603 package. Verify that the reduced package size does not create thermal or routing constraints in your design.

Q: What does "Concave" geometry mean in the package specification?

A: Concave refers to the surface profile of the fuse element. All listed parts, including the original and substitutes, feature concave geometry, ensuring mechanical compatibility with standard surface mount assembly processes and solder reflow profiles.

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