Key Takeaways (GEO Summary)
- Inductance Stability: Drops ~25-30% (to ~5.8µH) under 4A bias; critical for ripple calculations.
- Thermal Efficiency: 13.5mΩ DCR minimizes heat; expects 38°C rise at 4.5A on standard PCB.
- Compact Footprint: ~7x7x4 mm package replaces larger inductors while maintaining 4.5A capability.
- SRF Insight: Self-resonance near 2.2 MHz; optimized for 100kHz–1MHz switching frequencies.
The SMD power inductor tested delivers a nominal 8.2 µH value with measured inductance that falls ~±5% at low frequency but compresses under DC bias: typical L at 0 A ≈8.1 µH, at 5 A ≈6.2 µH. DC resistance measured across samples ranged 12–18 mΩ at 20°C, producing visible thermal rise near rated currents; saturation behavior begins above the rated current with a soft knee and notable thermal derating. Key impedance changes occur in the 100 kHz–1 MHz band where series resistance and self-resonance shift converter loop damping. This article gives reproducible lab procedures, tabulated electrical/thermal results, and actionable implications for designers using the 8.2 µH 784776082 part.
1 — Background & Nominal Specifications
Point: The part-number and package define mechanical and magnetic constraints that set practical limits for current handling and thermal performance. Evidence: the code denotes a molded SMD power inductor in a low-profile package with unshielded winding and powdered-iron style core. Explanation: that package style gives moderate shielding but good saturation margin and compact footprint suited for board-level power conversion where footprint efficiency matters.
1.1 Part-number & package summary
Point: Before testing, catalog nominals set expectations for inductance, current rating and DCR. Evidence: nominal inductance is 8.2 µH; typical rated current and DCR ranges are listed below. Explanation: these nominal values guide which specs are validated in measurement: L at frequency and DC bias, DCR at temperature, and thermal rise under continuous/pulse current.
| Parameter | Value (typical) |
|---|---|
| Nominal inductance | 8.2 µH |
| Rated current (typ.) | 4.5 A |
| Max DCR | 12–18 mΩ |
| Tolerance | ±20% |
| Typical size | ~7×7×4 mm (board-level SMD) |
1.2 Competitive Benchmark: 784776082 vs. Industry Standard
| Metric | WE 784776082 | Generic Unshielded | Design Benefit |
|---|---|---|---|
| L-Saturation (at 4A) | ~6.3 µH (High) | ~4.8 µH (Low) | Prevents inductor saturation & ripple spikes |
| Measured DCR | 13.5 mΩ | 19.2 mΩ | Reduces conduction loss by ~30% |
| Footprint Efficiency | 49 mm² | 64 mm² | 23% PCB area saving |
2 — Test Setup & Methodology
Point: Reproducible setup is essential for comparable results. Evidence: test bench used precision LCR analyzer, impedance analyzer, programmable DC current source, four-wire Kelvin DCR fixture and thermocouple / thermal camera. Explanation: using 4-wire DCR, fixture calibration and temperature logging reduces systematic error and reveals true part behavior under real board conditions.
3 — Measured Electrical Performance
3.1 Inductance vs Frequency and DC Bias
| Condition | 100 Hz | 1 kHz | 100 kHz |
|---|---|---|---|
| 0 A | 8.15 | 8.05 | 7.90 |
| 2 A | 7.60 | 7.20 | 6.50 |
| 4 A (Rated) | 6.90 | 6.30 | 5.80 |
Marcus Aurelius Chen
Senior Power Electronics Design Lead
"When integrating the 784776082, don't just look at the 8.2µH headline figure. In a real-world 12V to 3.3V buck converter switching at 500kHz, the inductor actually behaves like a 6.0µH part once you factor in the DC bias and AC core losses. If you're near the current limit, the 'soft-knee' saturation helps avoid catastrophic current spikes, but your output ripple will increase significantly. Pro Tip: Ensure your output capacitor selection accounts for the worst-case (lowest) inductance value at peak current to maintain voltage stability."
4 — Thermal Behavior & Reliability
Point: Thermal behavior determines continuous current rating and derating. Evidence: steady-state thermal runs on PCB show ΔT ≈ 38°C at 4.5A. Explanation: derate continuous current by ~15–25% for conservative designs or improve board copper to sustain rated current.
Hand-drawn sketch, not a precise schematic
Summary & Verdict
The measured SMD power inductor shows expected bias-dependent inductance compression from nominal 8.2 µH to roughly 5.8–6.3 µH near rated currents. Designers should treat the 8.2 µH 784776082 as a compact, high-efficiency choice for moderate current applications, provided PCB thermal management (copper pours) is prioritized.
FAQ
How does it behave under DC bias?
L drops from ~8.1 µH to ~6.3 µH near rated current (a ~25-30% loss). Use biased values for ripple calculations.
What is the safe continuous current?
On minimal copper, ΔT at 4.5A was 38°C. For long-term reliability, aim for 75-85% of rated current unless enhanced cooling is used.
