RLD30P300UFF Equivalent & Substitute Parts

Part Overview

The RLD30P300UFF is a Polymeric PTC Resettable Fuse manufactured by Littelfuse Inc., rated for 30V at 3A hold current with through-hole radial disc packaging. This component is classified as Obsolete, making identification of equivalent and substitute parts essential for ongoing design support and procurement continuity. Substitute parts maintain identical electrical specifications and mechanical compatibility while offering active product status and improved availability.

Key Parameters

Parameter	Value
Voltage - Max	30V
Current - Hold (Ih) (Max)	3 A
Current - Trip (It)	6 A
Time to Trip	10.8 s
Resistance - Initial (Ri) (Min)	20 mOhms
Resistance - Post Trip (R1) (Max)	80 mOhms
Operating Temperature	-40°C ~ 85°C
Mounting Type	Through Hole
Package / Case	Radial, Disc
Size / Dimension	0.449" L x 0.118" W (11.40mm x 3.00mm)
Lead Spacing	0.201" (5.10mm)
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

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

Voltage rating: 30V maximum
Current hold specification: 3A
Current trip specification: 6A
Trip time: 10.8 seconds
Initial and post-trip resistance values
Operating temperature range: -40°C to 85°C
Through-hole radial disc package configuration
Lead spacing and physical dimensions

All identified substitute parts meet these criteria. Variations in maximum current rating (40A vs. 100A), height-seated dimension, and approval agency certifications do not affect functional substitution for applications designed around the RLD30P300UFF specifications.

Parameter Comparison

Parameter	RLD30P300UFF	30R300UPR	RUEF300-AP	RUEF300K-AP
Manufacturer	Littelfuse Inc.	Littelfuse Inc.	Littelfuse	Littelfuse Inc.
Series	POLY-FUSE®, RLD30	POLY-FUSE®, 30R	PolySwitch®, RUEF	PolySwitch®, RUEF
Product Status	Obsolete	Active	Active	Active
Type	Polymeric	Polymeric	Polymeric	Polymeric
Voltage - Max	30V	30V	30V	30V
Current - Hold (Ih) (Max)	3 A	3 A	3 A	3 A
Current - Trip (It)	6 A	6 A	6 A	6 A
Current - Max	40 A	40 A	100 A	100 A
Time to Trip	10.8 s	10.8 s	10.8 s	10.8 s
Resistance - Initial (Ri) (Min)	20 mOhms	20 mOhms	20 mOhms	20 mOhms
Resistance - Post Trip (R1) (Max)	80 mOhms	80 mOhms	80 mOhms	80 mOhms
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	Radial, Disc	Radial, Disc	Radial, Disc	Radial, Disc
Size / Dimension	0.449" L x 0.118" W (11.40mm x 3.00mm)	0.449" L x 0.118" W (11.40mm x 3.00mm)	0.449" L x 0.118" W (11.40mm x 3.00mm)	0.449" L x 0.118" W (11.40mm x 3.00mm)
Height - Seated (Max)	0.681" (17.30mm)	0.756" (19.20mm)	0.650" (16.50mm)	0.650" (16.50mm)
Lead Spacing	0.201" (5.10mm)	0.201" (5.10mm)	0.199" (5.05mm)	0.199" (5.05mm)
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Approval Agency	cURus, TUV	cURus, TUV	CQC, CSA, TUV, UL	CQC, CSA, TUV, UL

Engineering Selection Recommendations

All three substitute parts (30R300UPR, RUEF300-AP, RUEF300K-AP) provide direct functional equivalence to the RLD30P300UFF across all critical electrical parameters. Selection should be based on the following factors:

30R300UPR maintains the closest dimensional profile to the original part with identical lead spacing (0.201") and represents the POLY-FUSE® series continuation. This part carries Active product status with 26,056 units in stock inventory.

RUEF300-AP and RUEF300K-AP are PolySwitch® series alternatives with expanded approval agency certifications (CQC, CSA, TUV, UL) compared to the original part. Both parts feature slightly reduced height-seated dimensions (0.650" vs. 0.681") and marginally tighter lead spacing (0.199" vs. 0.201"). Both carry Active product status with inventory availability of 3,851 and 2,998 units respectively.

All substitute parts are ROHS3 compliant and maintain identical electrical performance specifications. Selection among these options depends on PCB layout constraints, approval agency requirements for the end application, and inventory availability.

Frequently Asked Questions (FAQ)

Q: Can RLD30P300UFF be directly replaced with 30R300UPR?

A: Yes. The 30R300UPR maintains identical electrical specifications (30V, 3A hold, 6A trip, 10.8s trip time) and mechanical compatibility. Lead spacing and footprint are equivalent. The primary difference is product status (Active vs. Obsolete) and packaging format (Cut Tape vs. standard).

Q: What is the difference between RUEF300-AP and RUEF300K-AP?

A: Both parts are electrically and mechanically identical with matching 30V, 3A, and 6A specifications. The primary distinction is approval agency certification scope, with both parts carrying CQC, CSA, TUV, and UL approvals. No functional difference exists for standard applications.

Q: Are there height or lead spacing concerns when substituting?

A: Height-seated dimensions vary slightly (0.650" to 0.756" range), and lead spacing differs marginally (0.199" to 0.201"). These variations are within standard PCB design tolerances for through-hole radial components. Verify PCB layout clearances for applications with tight vertical or horizontal spacing constraints.

Q: Do all substitute parts meet RoHS compliance?

A: Yes. All substitute parts carry ROHS3 Compliant status, matching the original RLD30P300UFF specification.

Q: Which substitute part offers the best inventory availability?

A: The 30R300UPR offers the highest inventory level at 26,056 units in stock, followed by RUEF300-AP (3,851 units) and RUEF300K-AP (2,998 units).

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