MICROSMD150-2 Equivalent & Substitute Parts

Part Overview

The MICROSMD150-2 is a polymeric PTC resettable fuse manufactured by Littelfuse Inc., rated for 6V at 1.5A hold current in a 1210 (3225 Metric) surface mount package. This component is classified as obsolete, necessitating identification of active equivalent parts for new designs and ongoing production requirements. Substitute parts must maintain identical electrical ratings and mechanical compatibility to ensure direct board-level replacement without circuit redesign.

Key Parameters

Parameter	Value
Voltage - Max	6V
Current - Hold (Ih) (Max)	1.5 A
Current - Trip (It)	3 A
Current - Max	40 A
Resistance - Initial (Ri) (Min)	40 mOhms
Resistance - Post Trip (R1) (Max)	110 mOhms
Operating Temperature	-40°C ~ 85°C
Package / Case	1210 (3225 Metric), Concave
Mounting Type	Surface Mount
Type	Polymeric

Substitute Part Grouping Explanation

Substitution eligibility is determined by strict equivalence across the following critical parameters:

Voltage rating: 6V maximum
Current hold (Ih): 1.5A maximum
Current trip (It): 3A
Package: 1210 (3225 Metric), Concave surface mount
Operating temperature range: -40°C to 85°C
Polymeric PTC type construction

Two active substitute parts meet these criteria: MICROSMD150F-2 (Littelfuse) and MF-USMF150-2 (Bourns). Both maintain identical electrical performance specifications and mechanical footprint compatibility with the obsolete MICROSMD150-2.

Parameter Comparison

Parameter	MICROSMD150-2	MICROSMD150F-2	MF-USMF150-2
Manufacturer	Littelfuse Inc.	Littelfuse	Bourns Inc.
Product Status	Obsolete	Active	Active
Voltage - Max	6V	6V	6V
Current - Hold (Ih) (Max)	1.5 A	1.5 A	1.5 A
Current - Trip (It)	3 A	3 A	3 A
Current - Max	40 A	40 A	40 A
Resistance - Initial (Ri) (Min)	40 mOhms	40 mOhms	30 mOhms
Resistance - Post Trip (R1) (Max)	110 mOhms	110 mOhms	110 mOhms
Time to Trip	1 s	1 s	5 s
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C
Package / Case	1210 (3225 Metric), Concave	1210 (3225 Metric), Concave	1210 (3225 Metric), Concave
Mounting Type	Surface Mount	Surface Mount	Surface Mount
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant
Approval Agency	CSA, TUV, UL	CSA, TUV, UL	cURus, TUV
Thickness (Max)	0.048" (1.22mm)	0.048" (1.22mm)	0.033" (0.85mm)
Moisture Sensitivity Level (MSL)	2A (4 Weeks)	2A (4 Weeks)	1 (Unlimited)

Engineering Selection Recommendations

MICROSMD150F-2 is the primary substitute for MICROSMD150-2. Both components are from Littelfuse's PolySwitch microSMD series, share identical electrical specifications, and maintain the same 1-second trip time. MICROSMD150F-2 is active in production with ROHS3 compliance, addressing the obsolescence of the original part while preserving all functional parameters.

MF-USMF150-2 (Bourns Multifuse series) is a secondary substitute that meets all critical electrical and mechanical requirements. This part exhibits a longer 5-second trip time and lower initial resistance (30 mOhms versus 40 mOhms), which may affect circuit behavior in time-sensitive protection applications. MF-USMF150-2 offers superior moisture handling (MSL 1 versus 2A) and reduced package thickness (0.033" versus 0.048"), providing advantages in space-constrained designs. Both substitute parts carry ROHS3 compliance and appropriate regulatory certifications.

Frequently Asked Questions (FAQ)

Q: Can MICROSMD150F-2 replace MICROSMD150-2 without circuit modification?

A: Yes. MICROSMD150F-2 maintains identical voltage, current hold, current trip, and operating temperature specifications. The 1210 package footprint and surface mount configuration are mechanially and electrically compatible. No circuit redesign is required.

Q: What is the difference between MICROSMD150F-2 and MF-USMF150-2?

A: Both parts meet the core electrical requirements (6V, 1.5A hold, 3A trip). Key differences include trip time (1 second versus 5 seconds), initial resistance (40 mOhms versus 30 mOhms), package thickness (0.048" versus 0.033"), and moisture sensitivity rating. The longer trip time of MF-USMF150-2 may be unsuitable for circuits requiring rapid fault response.

Q: Are both substitute parts RoHS compliant?

A: Yes. MICROSMD150F-2 and MF-USMF150-2 are both ROHS3 compliant, addressing environmental regulations that the obsolete MICROSMD150-2 does not meet.

Q: Which substitute should I select for new designs?

A: MICROSMD150F-2 is recommended for direct replacement applications due to identical trip time and resistance characteristics. MF-USMF150-2 is suitable when extended trip time and improved moisture handling are acceptable or beneficial to the application.

Q: Are the package dimensions identical across all three parts?

A: The footprint (1210 / 3225 Metric) and length/width dimensions are identical. Package thickness differs: MICROSMD150-2 and MICROSMD150F-2 are 0.048" maximum, while MF-USMF150-2 is 0.033" maximum. Verify PCB assembly clearance if space constraints exist.

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