Part A
0451005.MRL
Littelfuse Inc.
- Lifecycle
- Active
- Stock
- 6135 Stückzahl
- Package
- 2-SMD
- Series
- Sicherungen
Replacement verdict
Compatible functional replacement candidate
The 0451001.MRL and 0451005.MRL are both surface-mount slow-blow ceramic fuses from the Littelfuse 451 series, sharing identical package, voltage rating, and operating temperature characteristics. The primary distinction is the current rating, which directly affects overcurrent protection behavior. While the 0451005.MRL can serve as a higher-current alternative in circuits designed with adequate margin, it is not a direct drop-in replacement for the 0451001.MRL without verifying the application's protection requirements.
Current Rating
Validation required
Package Type
High match
Voltage Rating
High match
Operating Temperature
High match
Parts at a glance
Part B
0451001.MRL
Littelfuse Inc.
- Lifecycle
- Active
- Stock
- 7334 Stückzahl
- Package
- 2-SMD
- Series
- Sicherungen
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 0451001.MRL | 0451005.MRL | Why it matters |
|---|---|---|---|
| Current Rating | 1 A | 5 A | Determines the maximum continuous current the fuse can carry without opening; a direct functional substitutability constraint. |
| Voltage Rating (DC) | 125 V | 125 V | Specifies the maximum DC voltage the fuse can safely interrupt; must meet or exceed the circuit voltage. |
| Voltage Rating (AC) | 125 V | 125 V | Specifies the maximum AC voltage the fuse can safely interrupt; relevant for AC circuit protection. |
| Interrupting Rating | 50 A at 125 VAC / 50 A at 125 VDC | 50 A at 125 VAC / 50 A at 125 VDC | Indicates the maximum fault current the fuse can safely break without damage or hazard. |
| Nominal Melting I²t | 0.42 A²s | 21.6 A²s | Represents the energy required to melt the fuse element; affects opening speed under overcurrent conditions. |
| Nominal Voltage Drop | 0.135 V | 0.115 V | Lower voltage drop reduces power loss and heat generation in the circuit during normal operation. |
| Nominal Cold Resistance | 0.135 Ohm | 0.023 Ohm | Affects inrush current behavior and steady-state power dissipation; lower resistance is preferable for higher currents. |
| Fuse Type | Fast-Acting (Nano2) | Fast-Acting (Nano2) | Defines the time-current characteristic; fast-acting fuses respond quickly to overcurrents to protect sensitive components. |
| Package / Size | Nano2, 6.1 mm x 2.69 mm | Nano2, 6.1 mm x 2.69 mm | Physical dimensions and footprint must match for drop-in replacement on the PCB. |
| Operating Temperature Range | -55°C to +125°C | -55°C to +125°C | Ensures reliable operation and proper derating across the application's environmental conditions. |
Need help validating a replacement?
Send your BOM and application constraints for technical and sourcing review.
Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 0451005.MRL | 0451001.MRL |
|---|---|---|
| Series | NANO²® 451 | NANO²® 451 |
| Part Status | Active | Active |
| Mounting Type | Surface Mount | Surface Mount |
| Fuse Type | Board Mount (Cartridge Style Excluded) | Board Mount (Cartridge Style Excluded) |
| Current Rating (Amps) | 5 A | 1 A |
| Voltage Rating - AC | 125 V | 125 V |
| Voltage Rating - DC | 125 V | 125 V |
| Response Time | Fast Blow | Fast Blow |
| Breaking Capacity @ Rated Voltage | 50A | 50A |
| Melting I²t | 5.566 | 0.459 |
| Approval Agency | CSA, PSE, UL | CSA, PSE, UL |
| Operating Temperature | -55°C ~ 125°C | -55°C ~ 125°C |
Frequently asked questions
What are the 0451001.MRL and 0451005.MRL fuses?
The 0451001.MRL and 0451005.MRL are surface-mount fuses from Littelfuse's 451 series, a family of very fast-acting, high-voltage-rated ceramic fuses. The 0451001.MRL is rated 1 A and the 0451005.MRL is rated 5 A, both at 125 VAC/VDC with a breaking capacity of 50 A at 125 VAC/VDC.
What is the main difference between the 0451001.MRL and 0451005.MRL?
The primary difference is the current rating: the 0451001.MRL is rated for 1 A, while the 0451005.MRL is rated for 5 A. Both share the same 451 series platform, including the same 125 VAC/VDC voltage rating, 50 A breaking capacity, very fast-acting characteristic, and surface-mount package footprint.
Are the 0451001.MRL and 0451005.MRL interchangeable in a design?
No, they are not directly interchangeable because their current ratings differ by a factor of five. Substituting a 1 A fuse with a 5 A fuse (or vice versa) changes the overcurrent protection threshold and can compromise circuit safety or cause nuisance opening. Any substitution must be validated against the application's normal operating current, inrush profile, and the fuse's time-current characteristics.
What is the voltage and breaking capacity rating of these fuses?
Both the 0451001.MRL and 0451005.MRL are rated 125 VAC/VDC with a breaking capacity of 50 A at 125 VAC/VDC. These ratings are specified in the Littelfuse 451 series datasheet and should not be exceeded in the application.
What is the interrupting rating and typical applications for the 451 series?
The 451 series has a 50 A interrupting rating at 125 VAC/VDC. Typical applications include primary and secondary circuit protection in equipment such as battery chargers, power supplies, consumer electronics, and industrial control equipment where a compact, very fast-acting surface-mount fuse is required.
What package and mounting type do the 0451001.MRL and 0451005.MRL use?
Both fuses are surface-mount devices in a ceramic body package. The 451 series is supplied in a compact SMD form factor suitable for automated pick-and-place assembly and reflow soldering. Designers should consult the Littelfuse 451 series datasheet for exact body dimensions, pad layout, and recommended soldering profile.
What is the operating temperature range for these fuses?
The Littelfuse 451 series is specified for operation over a temperature range of -55 °C to +125 °C. Fuse current-carrying capacity may be derated at elevated ambient temperatures, so the manufacturer's temperature derating curves should be applied when operating near the upper limit.
Do the 0451001.MRL and 0451005.MRL carry any agency approvals?
The Littelfuse 451 series is recognized under UL and certified by CSA, and it also carries VDE approval, as stated in the manufacturer's datasheet. Designers should verify the specific approval file numbers and any applicable conditions directly from the latest Littelfuse documentation before finalizing a design.