Product Overview & Typical Applications
Primary Function: Functions as a board-level overcurrent protection element for low-power rails and inrush-prone inputs. Commonly deployed on 5 V and 12 V rails, USB-style inputs, and small power supplies.
Design Advantage: Its time-delay characteristic allows the fuse to tolerate short inrush events (motors, capacitors) while effectively protecting steady-state circuits. The compact Nano-2 SMD form factor is ideal for high-density consumer PCBs and industrial modules.
Key Feature Summary & Trade-offs
Slow-Blow Profile
Tolerates startup surges; avoids nuisance blowing during initial capacitor charging or motor startup.
Compact Footprint
Nano-2 SMD dimensions allow for significant space savings in tightly packaged modern electronics.
Trade-off Note
Slower clearing time and higher I²t compared to fast-acting fuses. Not suitable for instantaneous short suppression.
Electrical Specifications — Ratings & Limits
| Parameter | Example Value | Unit | Status |
|---|---|---|---|
| Rated Current (In) | 1 | A | [VERIFY] |
| Rated Voltage | 125 | VAC / VDC | [VERIFY] |
| Breaking Capacity | 50 | A @ rated V | [VERIFY] |
| Cold Resistance | ~225 | mΩ | [VERIFY] |
| Melting I²t | ~1.98 | A²s | [VERIFY] |
Melting I²t Visual Capability
Typical Inrush Withstand vs Standard Fast-Blow Fuses
0452001.MRL (Slow-Blow)1.98 A²s
Standard Fast-Blow Fuse~0.45 A²s
Mechanical & Mounting
- Dimensions: Verify overall L×W×H against Nano-2 package standards.
- PCB Footprint: Use recommended land patterns with ±0.1 mm tolerances.
- Reflow: Follow standard lead-free profiles; ensure consistent solder volume to prevent tombstoning.
Thermal Constraints
- Derating: Continuous current should be derated when ambient temp exceeds 25°C.
- Heat Sinking: Increase copper pour area and use via stitching under pads.
- Placement: Avoid proximity to high-power components like MOSFETs or inductors.
Performance Testing & Reliability
Standard Test Procedures
To be documented for design acceptance:
- Time-Current Verification (1×, 2×, 3× In)
- Breaking Capacity Test at rated voltage
- Thermal Shock & Humidity Cycling
- Resistance change after lifecycle testing
Troubleshooting Failure Modes
- Discoloration/Cracking: Sign of severe overstress or improper reflow profile.
- High Resistance: Indicates partial melting or cumulative surge fatigue.
- Early Opening: Check for excessive ambient temperature or insufficient derating.
Design Selection & Procurement Checklist
Rating Selection Flow
- Define max continuous steady-state current.
- Estimate peak inrush current and duration.
- Apply Rule-of-Thumb: Steady-state current ≤ 80% of In.
- Confirm breaking capacity exceeds system fault current.
Quality Control Checklist
- Verify Lot Traceability and Manufacturer Test Reports.
- Confirm shelf life and moisture sensitivity level (MSL).
- Perform incoming resistance spot checks (mΩ).
- Validate T-I curve against system trip requirements.
Key Summary
- Rated performance: Specify In, Vac/Vdc, and breaking capacity; example In = 1 A and breaking capacity ≈ 50 A must be verified.
- Time-delay behavior: Include a T–I curve and list guaranteed open times at 1×, 2×, 3× In to ensure acceptable inrush tolerance.
- Mechanical & Thermal: Publish exact L×W×H and derating curves; isolate from heat sources using copper pours.
- Procurement: Require lot traceability and incoming resistance tests to preserve solderability and performance.
