Littelfuse 02331.25M Glass Cartridge Fuse Equivalent & Substitute Parts

Part Overview

The Littelfuse 02331.25M is a 1.25 A, 125 V AC/DC glass cartridge fuse in 5mm x 20mm form factor with medium blow response time. This part is classified as obsolete, making equivalent substitute parts necessary for ongoing design support and procurement. The fuse requires a holder for installation and is rated for breaking capacity of 10 kA at rated voltage. Substitute parts maintain identical electrical and mechanical specifications while offering improved compliance status and active product availability.

Key Parameters

Parameter	Value
Current Rating	1.25 A
Voltage Rating (AC)	125 V
Fuse Type	Cartridge, Glass
Package / Case	5mm x 20mm
Response Time	Medium Blow
Breaking Capacity @ Rated Voltage	10 kA
Operating Temperature Range	-55°C to 125°C
Mounting Type	Requires Holder

Substitute Part Grouping Explanation

Substitute parts for the 02331.25M are qualified based on the following mandatory parameters:

Current Rating: 1.25 A (exact match required)
Voltage Rating (AC): 125 V (exact match required)
Package / Case: 5mm x 20mm (exact match required)
Fuse Type: Cartridge, Glass (exact match required)
Response Time: Medium Blow (exact match required)
Breaking Capacity @ Rated Voltage: 10 kA (exact match required)
Operating Temperature Range: -55°C to 125°C (exact match required)
Mounting Type: Requires Holder (exact match required)

All three substitute parts meet these criteria. Differences in secondary parameters such as melting I²t, DC cold resistance, and approval agency certifications do not affect functional substitutability within the specified electrical and mechanical constraints.

Parameter Comparison

Parameter	02331.25M (Main)	02331.25MXP	02331.25MXBP	02321.25MX125P
Manufacturer	Littelfuse Inc.	Littelfuse Inc.	Littelfuse Inc.	Littelfuse Inc.
Series	233	233	233	232
Product Status	Obsolete	Active	Active	Active
Current Rating (Amps)	1.25 A	1.25 A	1.25 A	1.25 A
Voltage Rating - AC	125 V	125 V	125 V	125 V
Response Time	Medium Blow	Medium Blow	Medium Blow	Medium Blow
Package / Case	5mm x 20mm	5mm x 20mm	5mm x 20mm	5mm x 20mm
Breaking Capacity @ Rated Voltage	10 kA	10 kA	10 kA	10 kA
Operating Temperature	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C
Mounting Type	Requires Holder	Requires Holder	Requires Holder	Requires Holder
Fuse Type	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Approval Agency	CSA, K-MARK, METI, UL	CE, CSA, KC, PSE, UL	CE, CSA, KC, PSE, UL	CE, KC, PSE
Inventory Status	1161 Pcs New Original In Stock	1718 Pcs New Original In Stock	732 Pcs New Original In Stock	692 Pcs New Original In Stock

Engineering Selection Recommendations

All three substitute parts are functionally equivalent to the 02331.25M and are qualified for direct replacement based on electrical and mechanical parameters.

02331.25MXP is the primary substitute. It maintains Series 233 continuity with the original part, carries active product status, and holds comprehensive approval certifications including CE, CSA, KC, PSE, and UL. ROHS3 compliance is achieved. Inventory availability is highest at 1718 pieces.

02331.25MXBP is an alternative substitute within Series 233. It provides identical electrical performance and active product status with equivalent certification coverage (CE, CSA, KC, PSE, UL) and ROHS3 compliance. Inventory is available at 732 pieces.

02321.25MX125P represents a cross-series substitute from Series 232. While electrically and mechanically equivalent, it carries a reduced certification set (CE, KC, PSE only, excluding CSA and UL). This part is suitable for applications where CSA and UL certifications are not required. Inventory is available at 692 pieces.

For applications requiring full certification coverage (CSA and UL), select either 02331.25MXP or 02331.25MXBP. For applications with reduced certification requirements, 02321.25MX125P is acceptable.

Frequently Asked Questions (FAQ)

Q: Can the 02331.25MXP directly replace the obsolete 02331.25M?

A: Yes. The 02331.25MXP is a direct functional equivalent. Both parts share identical current rating (1.25 A), voltage rating (125 V AC), package dimensions (5mm x 20mm), response time (medium blow), and breaking capacity (10 kA). Physical installation in existing fuse holders is identical.

Q: What is the difference between the three substitute parts?

A: All three substitutes meet the mandatory electrical and mechanical parameters. The primary differences are product series (233 vs. 232), approval certifications, and inventory levels. The 02331.25MXP and 02331.25MXBP remain in Series 233 with comprehensive certifications. The 02321.25MX125P is Series 232 with reduced certifications (no CSA or UL).

Q: Does the 5mm x 20mm package dimension apply to all substitutes?

A: Yes. All substitute parts use the identical 5mm x 20mm cartridge form factor and require the same fuse holder type. No mechanical redesign or holder replacement is necessary.

Q: Are all substitutes RoHS compliant?

A: Yes. All three substitute parts are ROHS3 compliant, whereas the original 02331.25M is RoHS non-compliant. This represents an improvement in environmental compliance.

Q: Which substitute should be selected for applications requiring UL certification?

A: Both 02331.25MXP and 02331.25MXBP carry UL approval. The 02321.25MX125P does not include UL certification and should not be used in applications where UL approval is mandatory.

Q: Are there inventory or lead time considerations?

A: All three substitutes are in active production with current inventory. The 02331.25MXP has the highest inventory level at 1718 pieces, followed by 02331.25MXBP at 732 pieces and 02321.25MX125P at 692 pieces.

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