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Littelfuse 045903.5UR 3.5 A Very Fast-Acting (FF) PICO® SMF 459 – Tape & Reel UR
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pLittelfuse 045903.5UR — integrated circuit, PICO® SMF surface-mount fuse; Tape amp; Reel, 125 V./p
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Littelfuse 045903.5UR 3.5 A Very Fast-Acting (FF) PICO® SMF 459 – Tape & Reel UR
The 045903.5UR from Littelfuse carries 3.5 A, rated 125 VAC/VDC, uses a fast-acting element.
Technical Data
| Parameter | Rating |
|---|---|
| Parameter | Value |
| Manufacturer / Series | Littelfuse / PICO® SMF 459 |
| Part number | 045903.5UR |
| Fuse characteristic | Very Fast-Acting (FF) |
| Rated current | 3.5 A |
| Rated voltage | 125 VAC/VDC |
| Interrupting capability | 50 A @ 125 VAC; 300 A @ 125 VDC |
| Package | PICO® SMF surface-mount fuse; Tape & Reel |
| Mounting method | Surface Mount (SMD) |
| Dimensions | 8.26 × 4.32 × 3.05 mm |
| Lead pitch | N/A (SMD) |
| Operating temperature | -55°C to +125°C |
| Approvals | UL E10480; CSA 29862; PSE NBK030205-E10480B |
| Standards / compliance | UL Recognized; CSA (rating-dependent); PSE (1–5A); RoHS |
| Environmental | RoHS compliant |
| Nominal cold resistance | 0.0233 Ω |
| Nominal melting I²t | 1.65 A²s |
| Packaging / order code | UR: Tape & Reel, 500 pcs; SMD terminals |
| Product status | Verify current orderability with Littelfuse / authorized distribution |
Practical Notes
- Interrupting capability is 50 A @ 125 VAC; 300 A @ 125 VDC — confirm the circuit's prospective fault current stays below this.
- Fast element suits resistive and semiconductor loads rather than motors with high inrush.
- Because it opens within milliseconds, downstream semiconductors see less let-through energy.
- Working voltage must stay at or below 125 VAC/VDC; a lower-rated part is not a safe substitute.
- Do not upsize beyond 3.5 A to stop nuisance trips — fix the cause instead.
Application Scenarios
Common installation contexts include:
- EV
- telecom
Buying Notes
Order code 045903.5UR from Littelfuse, supplied in PICO® SMF surface-mount fuse; Tape & Reel. Confirm the exact suffix before release.
Questions and Answers
What are the ratings of the 045903.5UR?
3.5 A continuous at 125 VAC/VDC, interrupting rating 50 A @ 125 VAC; 300 A @ 125 VDC.
Is the 045903.5UR fast-acting or time-delay?
It is fast-acting. Expect it to open quickly on overload.
Can the 045903.5UR be used on a higher fault-current circuit?
No — its interrupting rating is 50 A @ 125 VAC; 300 A @ 125 VDC. Choose a part whose breaking capacity exceeds the prospective fault current.
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