RUEF300 PolySwitch® Resettable PPTC – Complete Technical & Packaging Summary
(Extracted from Littelfuse RUEF Series datasheet, Rev. 10/22/18)

1. Device Overview• Type: Radial-leaded, resettable PPTC (Polymeric Positive-Temperature-Coefficient) over-current protector• Voltage rating: 30 VDC / 30 VAC RMS• Hold current (IH @ 20 °C): 3.0 A• Trip current (IT @ 20 °C): 6.0 A• Agency recognition: UL E74889, CSA 78165, TÜV, CQC
2. Electrical Characteristics (25 °C still air unless noted)Parameter | Symbol | Value | Unit | Conditions---|---|---|---|---Max. continuous voltage | VMAX | 30 | VDC/VAC | –Max. interrupt voltage | VINT | 30 | VDC/VAC | –Max. fault current | IMAX | 100 | A | 30 V, TL = 20 °CTyp. power dissipation when tripped | PD | 2.0 | W | –Time-to-trip (min) | ttrip | 10.8 | s | 15 A fault, 20 °CInitial resistance (as supplied) | RMIN – RMAX | 0.020 – 0.050 | Ω | 20 °CPost-trip resistance (1 h after reflow/trip) | R1MAX | 0.08 | Ω | 20 °C
3. Thermal & Environmental Data• Operating ambient: –40 °C to +85 °C• Storage: ≤ 40 °C, ≤ 70 % RH, sealed bags• Passive aging: ±5 % ΔR after 1 000 h @ 70 °C or 85 °C• Humidity aging: ±5 % ΔR, 85 °C / 85 % RH, 1 000 h• Thermal shock: ±5 % ΔR, 85 °C ↔ –40 °C, 10 cycles• Moisture sensitivity: J-STD-020 Level 1 (unlimited floor-life)
4. Mechanical / Physical Data• Lead material: Tin-plated copper, 0.52 mm² (≈ 20 AWG), Ø 0.81 mm• Device mass: 0.516 g (typ.)• Body dimensions: see Fig. 2 outline– A (width): 11.4 mm max– B (height): 16.5 mm max– C (thickness): 5.8 mm max– Lead spacing (F): 5.05 mm ± 0.75 mm• Flammability: UL 94 V-0 epoxy polymer• Solderability: ANSI/J-STD-002 Cat. 3, withstands 10 s @ 260 °C
5. Temperature Rerating Table (IH vs Tamb)Tamb (°C) | –40 | –20 | 0 | 20 | 25 | 40 | 50 | 60 | 70 | 85IH (A) | 4.35 | 3.90 | 3.45 | 3.00 | 2.91 | 2.49 | 2.31 | 2.04 | 1.83 | 1.56
6. Time-to-Trip Curve (20 °C)• 100 A fault: < 0.1 s• 30 A fault: ≈ 0.3 s• 15 A fault: 10.8 s (specification point)• 10 A fault: ≈ 30 s
7. Packaging & Shipping OptionsBag (standard) | Tape & Reel | Ammo Pack---|---|---Orderable suffix | (none) | ‑2 | ‑APPieces per inner pack | 500 | 2 500 | 1 000Standard carton qty | 10 000 | 12 500 | 5 000Part marking | U300 | U300 | U300
8. Tape & Reel Specifications (-2 suffix)• Carrier tape width: 18 mm• Device pitch: 12.7 mm• Reel diameter: 370 mm max• Reel width: 56 mm max• Sprocket holes: 4 mm Ø, 12.7 mm pitch• Moisture seal: dry-pack not required (MSL-1)
9. Typical Applications• USB hubs & peripherals • IEEE-1394 ports • HDD & CD-ROM drives• Set-top boxes • Battery packs (3-cell Li-ion, 12 V lead-acid)• Industrial controls • 24 VDC sensor rails • Motor control boards
10. Design-in Guidelines• Maintain ≥ 20 % derate on IH at highest ambient temperature• Avoid rigid potting or housings that restrict device expansion• Do not expose to silicone oils or aggressive solvents• Allow 0.5 mm extra board height for body expansion during trip• Series inductance > 10 µH may generate L·di/dt > 30 V – add clamp
11. Ordering SummaryStandard bag: RUEF300Tape & reel: RUEF300-2Ammo pack: RUEF300-APAll variants carry identical electrical performance; choice depends on high-volume assembly method.