SMD250-2 Polymeric PTC Resettable Fuse Equivalent & Substitute Parts

Part Overview

The SMD250-2 is a Polymeric PTC Resettable Fuse manufactured by Littelfuse Inc., rated for 15V at 2.5A hold current in a 2-SMD surface mount package. This component is classified as Obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Polymeric PTC resettable fuses provide automatic overcurrent protection by increasing resistance when current exceeds the trip threshold, then resetting when the fault condition clears. The SMD250-2 is designed for applications requiring compact surface mount protection in the 2.5A range.

Key Parameters

Parameter	Value
Voltage - Max	15V
Current - Hold (Ih) (Max)	2.5 A
Current - Trip (It)	5 A
Resistance - Initial (Ri) (Min)	35 mOhms
Resistance - Post Trip (R1) (Max)	85 mOhms
Operating Temperature	-40°C ~ 85°C
Mounting Type	Surface Mount
Package / Case	2-SMD
Time to Trip	25 s

Substitute Part Grouping Explanation

Substitution eligibility for the SMD250-2 is determined by the following critical parameters:

Voltage rating must be equal to or greater than 15V
Current hold (Ih) rating must be 2.5A
Current trip (It) rating must be 5A
Resistance characteristics (Ri and R1) must fall within acceptable tolerance
Operating temperature range must encompass -40°C to 85°C
Mounting type must be Surface Mount
Package footprint must be compatible with 2-SMD or equivalent form factor

Three substitute parts meet these criteria: SMD250F-2 (Littelfuse), MF-SM250-2 (Bourns), and 0ZCF0250FF2C (Bel Fuse). Each maintains the core electrical specifications while offering different packaging, compliance status, and performance characteristics.

Parameter Comparison

Parameter	SMD250-2 (Main)	SMD250F-2	MF-SM250-2	0ZCF0250FF2C
Manufacturer	Littelfuse Inc.	Littelfuse Inc.	Bourns Inc.	Bel Fuse Inc.
Voltage - Max	15V	15V	15V	16V
Current - Hold (Ih) (Max)	2.5 A	2.5 A	2.5 A	2.5 A
Current - Trip (It)	5 A	5 A	5 A	5 A
Current - Max	40 A	40 A	100 A	100 A
Time to Trip	25 s	25 s	25 s	16 s
Resistance - Initial (Ri) (Min)	35 mOhms	35 mOhms	24 mOhms	25 mOhms
Resistance - Post Trip (R1) (Max)	85 mOhms	85 mOhms	85 mOhms	85 mOhms
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Package / Case	2-SMD	2-SMD	2-SMD	2920 (7351 Metric), Concave
Product Status	Obsolete	Active	Active	Active
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Approval Agency	CSA, TUV, UL	CSA, TUV, UL	cURus, TUV (AEC-Q200)	AEC-Q200, cURus, TUV
Moisture Sensitivity Level (MSL)	2A (4 Weeks)	2A (4 Weeks)	1 (Unlimited)	2A (4 Weeks)

Engineering Selection Recommendations

SMD250F-2 (Littelfuse Inc.) is the primary direct substitute. It maintains identical electrical specifications and 2-SMD package footprint as the obsolete SMD250-2. The SMD250F-2 is Active status with ROHS3 compliance, making it suitable for new designs and legacy system replacements where package compatibility is critical.

MF-SM250-2 (Bourns Inc.) provides an alternative with enhanced performance characteristics. It offers lower initial resistance (24 mOhms vs. 35 mOhms), higher maximum current rating (100A vs. 40A), and superior moisture sensitivity (MSL 1 vs. 2A). The MF-SM250-2 includes AEC-Q200 automotive qualification and maintains the 2-SMD package form factor. This part is suitable for applications requiring automotive-grade reliability.

0ZCF0250FF2C (Bel Fuse Inc.) is a functional equivalent with different package geometry (2920 Metric vs. 2-SMD). It provides 16V voltage rating, faster trip time (16s vs. 25s), and AEC-Q200 qualification. This part requires PCB layout modification due to package size difference (7.36mm x 5.12mm vs. 8.70mm x 6.36mm) and reduced thickness (0.90mm vs. 3.00mm). Selection of this part is appropriate only when package footprint redesign is feasible.

All three substitutes maintain the critical 2.5A hold current, 5A trip current, and 85 mOhms maximum post-trip resistance required for circuit protection function.

Frequently Asked Questions (FAQ)

Q: Can SMD250F-2 be used as a direct replacement for SMD250-2?

A: Yes. SMD250F-2 is electrically and mechanically identical to SMD250-2, with matching 2-SMD package footprint, voltage rating (15V), hold current (2.5A), and trip current (5A). No circuit or PCB modifications are required.

Q: What is the primary difference between MF-SM250-2 and SMD250-2?

A: MF-SM250-2 offers lower initial resistance (24 mOhms vs. 35 mOhms), higher maximum current capability (100A vs. 40A), and superior moisture sensitivity (MSL 1 vs. 2A). The 2-SMD package footprint remains compatible. MF-SM250-2 includes AEC-Q200 automotive qualification, which SMD250-2 does not.

Q: Why does 0ZCF0250FF2C have a different package size?

A: 0ZCF0250FF2C uses the 2920 Metric package (7.36mm x 5.12mm x 0.90mm) instead of the 2-SMD package (8.70mm x 6.36mm x 3.00mm). This results in a smaller, thinner component. PCB layout redesign is necessary for this substitution.

Q: Are all three substitutes RoHS compliant?

A: Yes. SMD250F-2, MF-SM250-2, and 0ZCF0250FF2C are all ROHS3 compliant. The original SMD250-2 is RoHS non-compliant.

Q: Which substitute is recommended for automotive applications?

A: Both MF-SM250-2 and 0ZCF0250FF2C carry AEC-Q200 automotive qualification. SMD250F-2 does not include this certification.

Q: What is the impact of different trip times (25s vs. 16s)?

A: Trip time determines how quickly the fuse responds to overcurrent conditions. SMD250-2 and SMD250F-2 trip in 25 seconds, while 0ZCF0250FF2C trips in 16 seconds. Faster trip time provides quicker fault response but may increase nuisance trip risk in circuits with high inrush current. Circuit design must accommodate the selected trip time.

Q: Can these parts be used interchangeably on the same PCB?

A: SMD250F-2 can be used interchangeably with SMD250-2 without PCB modification. MF-SM250-2 is compatible with the same 2-SMD footprint. 0ZCF0250FF2C requires PCB redesign due to different package dimensions and cannot be used on existing SMD250-2 layouts without modification.

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