RHE450 Equivalent & Substitute Parts

Part Overview

The RHE450 is a polymeric PTC resettable fuse manufactured by Littelfuse Inc., rated for 16V and 4.5A hold current. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The RHE450 operates as a thermal protection device, automatically resetting after a fault condition is cleared, and is designed for through-hole radial mounting in disc configuration.

Key Parameters

Parameter	Value
Voltage - Max	16V
Current - Hold (Ih) (Max)	4.5 A
Current - Trip (It)	7.8 A
Current - Max	100 A
Time to Trip	3 s
Resistance - Initial (Ri) (Min)	22 mOhms
Mounting Type	Through Hole
Package / Case	Radial, Disc
Size / Dimension	0.409" L x 0.118" W (10.40mm x 3.00mm)
Lead Spacing	0.199" (5.05mm)

Substitute Part Grouping Explanation

Substitute parts for the RHE450 are identified based on electrical and mechanical parameter compatibility. The critical substitution criteria are:

Voltage rating of 16V maximum
Hold current (Ih) of 4.5A maximum
Trip current (It) of 7.8A
Maximum current capacity of 100A
Time to trip of 3 seconds
Initial resistance minimum of 22 mOhms
Through-hole radial disc mounting configuration
Physical dimensions of 0.409" L x 0.118" W (10.40mm x 3.00mm)

Two active substitute parts meet these electrical and mechanical requirements: RHEF450 (Littelfuse Inc.) and MF-RHT450-0 (Bourns Inc.). Both maintain identical electrical performance specifications and physical form factors suitable for direct replacement in circuit designs originally specified for the RHE450.

Parameter Comparison

Parameter	RHE450	RHEF450	MF-RHT450-0
Manufacturer	Littelfuse Inc.	Littelfuse Inc.	Bourns Inc.
Product Status	Obsolete	Active	Active
Voltage - Max	16V	16V	16V
Current - Hold (Ih) (Max)	4.5 A	4.5 A	4.5 A
Current - Trip (It)	7.8 A	7.8 A	7.8 A
Current - Max	100 A	100 A	100 A
Time to Trip	3 s	3 s	3 s
Resistance - Initial (Ri) (Min)	22 mOhms	22 mOhms	22 mOhms
Mounting Type	Through Hole	Through Hole	Through Hole
Package / Case	Radial, Disc	Radial, Disc	Radial, Disc
Size / Dimension	0.409" L x 0.118" W (10.40mm x 3.00mm)	0.409" L x 0.118" W (10.40mm x 3.00mm)	0.409" L x 0.118" W (10.40mm x 3.00mm)
Height - Seated (Max)	0.614" (15.60mm)	0.614" (15.60mm)	0.614" (15.60mm)
Operating Temperature	Not specified	-40°C ~ 125°C	-40°C ~ 125°C
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant
Approval Agency	CSA, TUV, UR	CSA, TUV, UL	Not specified

Engineering Selection Recommendations

RHEF450 is the primary substitute for the RHE450. Both components are manufactured by Littelfuse Inc. within the PolySwitch® series, ensuring design continuity. The RHEF450 is actively produced and carries ROHS3 compliance, addressing regulatory requirements that the obsolete RHE450 does not meet. Approval certifications include CSA, TUV, and UL standards.

MF-RHT450-0 is an alternative substitute manufactured by Bourns Inc. within the Multifuse® series. This component meets all electrical and mechanical specifications and carries ROHS3 compliance. The MF-RHT450-0 includes AEC-Q200 automotive qualification rating. Lead spacing for the MF-RHT450-0 is 0.114" (2.90mm), which differs from the RHE450 and RHEF450 at 0.199" (5.05mm). This lead spacing difference requires PCB layout verification before implementation.

Frequently Asked Questions (FAQ)

Q: Can RHEF450 be used as a direct replacement for RHE450?

A: Yes. The RHEF450 matches all critical electrical parameters (16V, 4.5A hold current, 7.8A trip current, 3-second trip time) and physical dimensions (0.409" L x 0.118" W, 0.614" seated height, 0.199" lead spacing). No circuit modifications are required.

Q: What is the difference between RHE450 and RHEF450?

A: Both are Littelfuse PolySwitch® polymeric PTC resettable fuses with identical electrical ratings. The RHE450 is obsolete; RHEF450 is the active production equivalent. RHEF450 provides ROHS3 compliance and specified operating temperature range (-40°C ~ 125°C), which the RHE450 does not document.

Q: Can MF-RHT450-0 replace RHE450 in existing designs?

A: Electrical compatibility is confirmed. However, the MF-RHT450-0 has lead spacing of 0.114" (2.90mm) compared to RHE450's 0.199" (5.05mm). PCB footprint verification is required before substitution. If the PCB is designed for 0.199" lead spacing, the MF-RHT450-0 will not fit without layout modification.

Q: What packaging options are available?

A: RHEF450 is supplied in bag packaging. MF-RHT450-0 is supplied in bulk packaging. Packaging selection depends on procurement volume and inventory management requirements.

Q: Are there compliance differences between the substitutes?

A: RHEF450 and MF-RHT450-0 both carry ROHS3 compliance. RHEF450 holds CSA, TUV, and UL certifications. MF-RHT450-0 includes AEC-Q200 automotive qualification. The RHE450 is RoHS non-compliant and obsolete.

Q: What is the post-trip resistance specification?

A: RHE450 specifies post-trip resistance (R1) maximum of 3.6 Ohms. RHEF450 and MF-RHT450-0 specify 54 mOhms maximum. This represents improved performance in the substitute parts, with lower resistance after thermal trip events.

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