MF-USML270-2 Equivalent & Substitute Parts

Part Overview

The MF-USML270-2 is a polymeric PTC resettable fuse manufactured by Bourns Inc., rated for 6V maximum voltage with a 2.7A hold current. This component is designed for surface mount applications in the 1210 (3225 Metric) package format with a concave profile. The part is currently listed as obsolete, making identification of functionally equivalent alternatives necessary for ongoing design support and component procurement.

Key Parameters

Parameter	Value
Manufacturer	Bourns Inc.
Voltage - Max	6V
Current - Hold (Ih) (Max)	2.7 A
Current - Trip (It)	5.4 A
Resistance - Initial (Ri) (Min)	4 mOhms
Resistance - Post Trip (R1) (Max)	20 mOhms
Operating Temperature	-40°C ~ 85°C
Mounting Type	Surface Mount
Package / Case	1210 (3225 Metric), Concave
Thickness (Max)	0.024" (0.60mm)
Approval Agency	cURus, TUV
RoHS Status	ROHS3 Compliant
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution eligibility for the MF-USML270-2 is determined by the following critical parameters:

Voltage Rating: Maximum voltage must equal or exceed 6V to maintain circuit protection integrity.

Current Characteristics: Hold current (Ih) and trip current (It) must remain within acceptable operational ranges. The substitute MF-USML260/6-2 operates at 2.6A hold current and 5.2A trip current, representing a 3.7% reduction in hold current and 3.7% reduction in trip current compared to the original specification.

Resistance Profile: Initial resistance (Ri) and post-trip resistance (R1) determine circuit behavior during normal operation and fault conditions. Both parts maintain 4 mOhms minimum initial resistance; however, post-trip resistance differs (20 mOhms vs. 30 mOhms maximum).

Package Compatibility: Both parts utilize the 1210 (3225 Metric) surface mount package with concave profile, ensuring mechanical and electrical compatibility on existing PCB layouts.

Environmental and Compliance Requirements: Operating temperature range, RoHS compliance, and regulatory approvals (cURus, TUV) must match or exceed the original specification.

Parameter Comparison

Parameter	MF-USML270-2 (Main)	MF-USML260/6-2 (Substitute)
Manufacturer	Bourns Inc.	Bourns Inc.
Voltage - Max	6V	6V
Current - Hold (Ih) (Max)	2.7 A	2.6 A
Current - Trip (It)	5.4 A	5.2 A
Current - Max	50 A	50 A
Time to Trip	4 s	5 s
Resistance - Initial (Ri) (Min)	4 mOhms	4 mOhms
Resistance - Post Trip (R1) (Max)	20 mOhms	30 mOhms
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C
Mounting Type	Surface Mount	Surface Mount
Package / Case	1210 (3225 Metric), Concave	1210 (3225 Metric), Concave
Thickness (Max)	0.024" (0.60mm)	0.031" (0.80mm)
Approval Agency	cURus, TUV	cURus, TUV
RoHS Status	ROHS3 Compliant	ROHS3 Compliant
Product Status	Obsolete	Active

Engineering Selection Recommendations

The MF-USML260/6-2 is the designated substitute for the obsolete MF-USML270-2. Both components maintain identical voltage ratings, operating temperature ranges, and regulatory certifications (cURus, TUV approval, ROHS3 compliance). The substitute part is currently in active production status with confirmed inventory availability.

Electrical parameter variations between the two parts are minimal: hold current differs by 0.1A (3.7% reduction), and trip current differs by 0.2A (3.7% reduction). Post-trip resistance increases from 20 mOhms to 30 mOhms maximum. Time to trip extends from 4 seconds to 5 seconds.

Physical dimensions remain compatible for PCB layout purposes, with the substitute part measuring 0.031" (0.80mm) maximum thickness compared to 0.024" (0.60mm) for the original. This 0.007" (0.20mm) thickness increase remains within typical PCB assembly tolerances for surface mount components.

Frequently Asked Questions (FAQ)

Q: Can the MF-USML260/6-2 be used as a direct replacement for the MF-USML270-2?

A: Yes. Both parts share identical voltage ratings (6V), operating temperature ranges (-40°C to 85°C), package format (1210 Concave), and regulatory approvals. The substitute maintains functional equivalence within the specified electrical parameter tolerances.

Q: What are the differences in current ratings between these parts?

A: The MF-USML260/6-2 operates at 2.6A hold current and 5.2A trip current, compared to 2.7A and 5.4A respectively for the MF-USML270-2. These represent 3.7% reductions in both parameters. Applications requiring the exact original current thresholds should evaluate circuit margin requirements.

Q: Are there physical compatibility concerns?

A: Both parts use the 1210 (3225 Metric) surface mount package with concave profile. The substitute part is 0.007" (0.20mm) thicker (0.031" vs. 0.024" maximum thickness). This difference is within standard PCB assembly tolerances and does not affect mechanical fit or electrical performance.

Q: What is the significance of the post-trip resistance difference?

A: Post-trip resistance increases from 20 mOhms to 30 mOhms maximum. This parameter defines circuit behavior after the fuse has tripped. The 10 mOhms increase is within acceptable limits for polymeric PTC resettable fuse technology and does not compromise circuit protection function.

Q: Why is the original part listed as obsolete?

A: The MF-USML270-2 is no longer in active production. The MF-USML260/6-2 represents the current production equivalent within the Bourns Multifuse product line, offering equivalent functionality with active manufacturing support and inventory availability.

Q: Are regulatory certifications maintained?

A: Yes. Both parts carry identical approvals (cURus, TUV) and maintain ROHS3 compliance. No additional qualification or testing is required from a regulatory standpoint.

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