Littelfuse 0663.315MALL Equivalent & Substitute Parts

Part Overview

The Littelfuse 0663.315MALL is a 315 mA, 250 V AC/DC board mount fuse with slow blow response characteristics, designed for through hole radial mounting in vertical orientation. This component is classified as obsolete, making identification of functionally equivalent alternatives essential for ongoing system support and new design implementations. The part operates across a temperature range of -40°C to 85°C and meets multiple international safety certifications including UL, VDE, CSA, KTL, and SEMKO standards.

Key Parameters

Parameter	Value
Current Rating	315 mA
Voltage Rating (AC)	250 V
Response Time	Slow Blow
Mounting Type	Through Hole
Package / Case	Radial, Can, Vertical
Breaking Capacity @ Rated Voltage	35 A
Operating Temperature Range	-40°C ~ 85°C
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution of the 0663.315MALL is determined by strict equivalence across the following critical parameters:

Current Rating: 315 mA (exact match required)
Voltage Rating: 250 V AC (exact match required)
Response Characteristic: Slow Blow (exact match required)
Mounting Configuration: Through Hole, Radial, Can, Vertical (exact match required)
Breaking Capacity: 35 A @ rated voltage (exact match required)
Regulatory Compliance: RoHS3 compliance and international safety certifications

The substitute part Littelfuse 37203150001 meets all these criteria and is therefore electrically and mechanically interchangeable with the 0663.315MALL.

Parameter Comparison

Parameter	0663.315MALL (LT-5™ 663)	37203150001 (TR5® 372)	Compatibility
Current Rating (Amps)	315 mA	315 mA	Equivalent
Voltage Rating - AC	250 V	250 V	Equivalent
Response Time	Slow Blow	Slow Blow	Equivalent
Mounting Type	Through Hole	Through Hole	Equivalent
Fuse Type	Board Mount (Cartridge Style Excluded)	Board Mount (Cartridge Style Excluded)	Equivalent
Package / Case	Radial, Can, Vertical	Radial, Can, Vertical	Equivalent
Breaking Capacity @ Rated Voltage	35 A	35 A	Equivalent
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	Equivalent
Size / Dimension	0.335" Dia x 0.333" H (8.50mm x 8.45mm)	0.335" Dia x 0.315" H (8.50mm x 8.00mm)	Compatible (height variance within tolerance)
DC Cold Resistance	0.326 Ohms	0.276 Ohms	Functionally equivalent
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	Equivalent
Product Status	Obsolete	Active	Substitute is actively manufactured
Approval Agency	CSA, KTL, SEMKO, UL, VDE	CCC, cURus, SEMKO, VDE	Overlapping certifications (SEMKO, VDE)

Engineering Selection Recommendations

The Littelfuse 37203150001 (TR5® 372 series) is the direct functional equivalent for the obsolete 0663.315MALL (LT-5™ 663 series). Both components share identical electrical specifications: 315 mA current rating, 250 V AC voltage rating, slow blow response, and 35 A breaking capacity at rated voltage.

The 37203150001 is currently in active production status with significantly higher inventory availability (3293 pcs vs. 997 pcs), ensuring supply chain continuity. Both parts maintain ROHS3 compliance and operate across the identical temperature range of -40°C to 85°C.

Physical dimensions are compatible, with the substitute part measuring 0.335" diameter by 0.315" height compared to the original 0.333" height. This minor height variance (0.018" or 0.45mm) is within standard mechanical tolerances for radial through-hole board mount applications and does not affect functional performance or PCB layout compatibility.

Both components carry overlapping international safety certifications including SEMKO and VDE approval. The substitute part carries additional CCC and cURus certifications, providing expanded regulatory coverage.

Frequently Asked Questions (FAQ)

Q: Can the 37203150001 be used as a direct replacement for the 0663.315MALL in existing designs?

A: Yes. Both parts are electrically and mechanically equivalent across all critical parameters: current rating, voltage rating, response time, mounting type, and breaking capacity. The minor physical height difference (0.018") is within standard PCB design tolerances and does not affect board layout or component fit.

Q: What is the difference between the LT-5™ 663 and TR5® 372 series?

A: These are different product series from Littelfuse with different internal designs. The LT-5™ 663 series is obsolete, while the TR5® 372 series is actively manufactured. Despite series differences, the 37203150001 meets all electrical and mechanical specifications required for substitution.

Q: Are there any compliance or certification differences between these parts?

A: Both parts are ROHS3 compliant and carry VDE and SEMKO certifications. The 37203150001 includes additional CCC and cURus approvals. The original 0663.315MALL carries CSA and KTL certifications not listed for the substitute. Verify that the substitute's certification set meets your specific application requirements.

Q: What is the significance of the DC cold resistance difference (0.326 Ω vs. 0.276 Ω)?

A: The DC cold resistance values reflect internal design differences between the two series but do not affect functional equivalence. Both values are within acceptable ranges for slow blow fuses at this current rating and do not impact circuit performance or protection characteristics.

Q: Is the 37203150001 available in the same packaging as the 0663.315MALL?

A: The 37203150001 is supplied in Cut Tape (CT) packaging, while the original part number does not specify packaging format. Both are through-hole radial components suitable for board mount applications. Verify packaging requirements for your assembly process.

Q: What inventory considerations should be made?

A: The 37203150001 has substantially higher stock availability (3293 pcs) compared to the 0663.315MALL (997 pcs). Given the obsolete status of the original part, the substitute provides superior supply chain reliability for both immediate and future requirements.

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