Recent bench testing shows that measured inductance under DC bias and actual RDC values frequently determine real-world converter behavior more than nominal datasheet numbers. In practice, a power inductor that meets a catalog L at zero-bias can still underperform once biased and heated on-board. This report explains how to measure inductance and RDC, typical deviations, and practical actions for designers and buyers. Why Measured Inductance and RDC Matter Electrical Role in Power Converters Inductance and RDC set ripple magnitude, transient energy, peak currents, EMI, and copper losses. Ripple current ΔI relates inversely to L and switching frequency; I²R defines copper loss. DESIGN FORMULAS: ΔI = (Vsw · D) / (L · fsw) Pcu = I_RMS² · RDC Datasheet Definitions & Test Conditions Datasheets report inductance and RDC under specific test conditions (e.g., 25°C, specific frequency) that may not match system use. Missing DC-bias curves or unspecified fixture details cause discrepancies between lab values and real-world performance. * Recommendation: Always request L vs. DC-bias curves and fixture descriptions from suppliers. Data Patterns: Typical Measured Value Trends Inductance: Frequency and DC-Bias Core materials respond differently to bias. Ferrite cores often show pronounced L reduction under bias, while powdered cores tend to be more linear. TYPICAL L-DROP UNDER BIAS (%) Ferrite Core-35% Powdered Core-12% RDC: Variation with Temperature Copper's temperature coefficient (~0.4%/°C) raises RDC with heat. At high frequencies, skin and proximity effects increase effective resistance beyond DC RDC. Thermal Impact: A 50°C rise in temperature results in a ~20% increase in RDC. Designers must budget for realistic on-board resistance rather than catalog nominals. How to Measure Inductance and RDC Properly Required Equipment & Fixturing • LCR Meter: Covering low kHz to switching frequencies. • Kelvin Source-Meter: For precise RDC measurement (4-wire). • DC Bias Source: External current source for saturation testing. Step-by-Step Procedure 1 Precondition parts and perform Short/Open compensation. 2 Measure L at baseline and actual switching frequency. 3 Apply bias points (0%, 25%, 50%, 75%, 100% of Isat). Example Measured Report and Interpretation Bias Current (A) Nominal L (µH) Measured L (µH) Deviation (%) Measured RDC (mΩ) 0.0 (Baseline) 10.0 9.85 -1.5% 12.4 5.0 (50% Isat) 10.0 8.92 -10.8% 12.5 10.0 (100% Isat) 10.0 6.40 -36.0% 12.7 * Highlighted cells flag parts needing further review or larger design margins. Supplier Specification Template Inductance at specified DC bias points. RDC at 25°C via 4-wire Kelvin method. Acceptance: ±10% L, ±15% RDC. Required L vs. Bias curve data. Design Rules & Derating Assume 20-30% less L than nominal. Include measured RDC in copper-loss calcs. 20-50% saturation headroom for transients. Thermal vias under pads for heat dissipation. Summary Reality Check: Measured inductance under DC bias and measured RDC determine converter ripple, losses, and thermal behavior. Don't rely solely on datasheet nominals. Best Practices: Use LCR or impedance analyzers for sweeps and Kelvin micro-ohm methods for RDC. Apply standardized DC bias points. Action: Budget for reduced L (20–30% margin), include real RDC in I²R loss budgets, and require explicit vendor curves. Frequently Asked Questions What is the best way to measure inductance under DC bias? + Use an impedance analyzer or LCR meter with an external DC current source capable of supplying the desired bias while compensating for the DC offset. Ensure the meter supports the test frequency and apply four-wire connections for stability. How should RDC measurement be specified for procurement? + Specify RDC at 25°C measured by the four-wire (Kelvin) method. State the instrument model class or resolution, include measurement uncertainty, and require the sample size and acceptance criteria to prevent supplier ambiguity. How do measured deviations affect thermal estimates? + Measured increases in RDC increase I²R losses, which raise inductor temperature. Translate additional power loss into temperature rise using the inductor’s thermal resistance (ΔT = P_loss · θJA). If θJA is unknown, measure temperature rise at rated current during qualification.

Point: This report summarizes bench measurements and PCB validation results for a shielded power inductor family, establishing real-world impacts on converter efficiency and reliability. Evidence: In bench tests across 12 sample boards, measured inductance deviation averaged 3.8% vs. nominal and average temperature rise under rated current reached 28–35°C. Explanation: Those deviations materially influence loop stability, thermal margin, and long-term solder reliability, motivating the test methods and pass/fail criteria that follow. Point: The introduction frames key goals: validate published technical specs on target PCBs and define QA limits for production. Evidence: The measured dataset covers L vs. frequency and DC bias, four‑wire DCR, saturation, and thermal cycling on representative layouts. Explanation: Engineers can use the procedures here to replicate findings, quantify derating, and reduce field failures through standardized incoming inspection and layout rules. Background: Published specs & selection context (background introduction) Datasheet summary: nominal electrical & mechanical specs Point: The datasheet lists nominal values that drive selection and simulation. Evidence: Typical listed items include nominal inductance, tolerance, rated DC current, saturation current, DCR (max), recommended footprint/land pattern, operating temperature range, and typical temperature rise. Explanation: Those published values form the baseline for pass/fail comparisons during incoming inspection and PCB validation. Parameter Datasheet value Tolerance Nominal inductance 10 μH ±10% Rated DC current 6 A - Saturation current (Isat) 9 A - DCR (max) 12 mΩ - Application fit & selection trade-offs Point: Fit assessment ties technical specs to application domains such as buck converters, VRMs, and switching regulators. Evidence: Key tradeoffs include DC bias behavior (L drop at operating current), DCR versus heat generation, and package size versus current capacity. Explanation: Selection checklist below helps decide when this part suits a design versus when a lower-DCR or physically larger inductor is preferable. Checklist: Verify L@operating current ≥ required loop inductance; DCR budget vs. efficiency target; thermal margin on PCB copper; footprint fit and reflow profile compatibility. Measured electrical specifications: bench methods & data (data analysis) — 7847709033 Inductance vs. frequency and DC-bias Point: LCR and impedance analyzer sweeps characterize L(f) and L(I). Evidence: Use a calibrated impedance analyzer with a low‑inductance fixture, measure from 100 Hz to 1 MHz and in DC bias steps 0 A → rated current in 0.5 A increments. Explanation: Expected deliverables are L vs. I and L vs. f plots; acceptable L variation is typically within datasheet tolerance plus measured DC‑bias shift (e.g., total deviation ≤ ±15% under operating bias for stable loop design). DCR, saturation current, and temperature Point: DCR and saturation determine losses and headroom. Evidence: Perform four‑wire DCR at 25°C, ramp current to identify Isat (L drops to defined percentage), and apply rated current for thermal steady state while logging ΔT with thermocouples or a thermal camera. Explanation: Acceptable DCR should not exceed datasheet max by more than 10% on arrival; temperature rise at rated current should match or be below datasheet typical value. Bench Test Performance Metrics DCR @25°C (Measured: 11.5 mΩ / Limit: 12 mΩ) PASS L deviation (Measured: -8% / Limit: -15%) PASS Temp rise @ Rated I (Measured: 32°C / Limit: 40°C) PASS PCB tests & layout validation: test designs and EMI/thermal checks Test PCB design and measurement fixtures Point: PCB layout and fixturing affect measured thermal and EMI behavior. Evidence: Recommended test boards are single‑inductor boards with Kelvin pads, thermocouple solder pads, and optional ground-plane variants. Explanation: Test variants should include: minimal copper, full copper pour, and alternate via counts to quantify thermal conduction and EMI shielding effects. Design one part per board with standardized footprint and Kelvin pads. Provide thermocouple solder points and room for thermal-camera imaging. Include layout variants: no plane, split plane, and solid plane. EMI, reflow, and thermal cycle tests Point: Combined EMI and reliability tests reveal field risks. Evidence: Run conducted and radiated EMI scans, verify reflow profile, and perform thermal cycling (-40°C to +125°C). Explanation: Deliverables are switching-node oscilloscope traces, EMI spectra, and failure logs. Define failure criteria such as L shift >20% or DCR increase >20%. Test results: board-level case studies (case study) Buck converter: efficiency, noise, and thermal Point: A 5 V → 1.2 V buck with the tested part quantified system impacts. Evidence: Measured efficiency delta of -0.6% at 50% load, switching-node noise raised by 2–3 dB, and hotspot temperatures rose 6–8°C. Explanation: The main driver was DC‑bias L reduction and slightly higher DCR; remedies included minor loop compensation and copper pour increase. High-current power module: reliability Point: High-current pulses expose saturation and solder stresses. Evidence: Under 20 ms current pulses at 1.5× rated current, several samples showed temporary L collapse and solder fatigue. Explanation: Recommended derating of 20–30% for continuous operation and stricter solder inspection criteria for pulse‑heavy applications. Practical recommendations & test checklist for production Design guidelines and derating rules Point: Follow layout and derating practices to ensure field reliability. Evidence: Use generous copper, place 3–5 thermal vias under the pad, maintain 0.5 mm clearance, and derate continuous DC by 20%. Explanation: These rules reduce hotspot temperatures, improve solder reliability, and preserve inductance under bias for stable converter operation. Measurement checklist & pass/fail criteria Point: A concise QA matrix enables consistent incoming inspection. Evidence: Suggested numeric thresholds: DCR ≤ datasheet max +10%, L@100 kHz within ±15%, temp rise ≤ datasheet typical +10°C. Explanation: Store per‑lot CSV fields: part ID, lot, measured DCR, L@100kHz, temp rise, visual result, operator; sample size: 5 pcs per lot. Summary • Measured deviations show that 7847709033 typically matches nominal inductance within ~4% but exhibits DC-bias dependent L drop; verify L vs. I on target PCB to avoid instability. • Thermal behavior is a primary risk: expect 28–35°C rise at rated current; increase copper and via count or derate continuous current by ~20% for robust margins. • QA checklist and PCB tests are essential before volume assembly; record DCR, L@100kHz, and temp rise per lot to catch drift and assembly issues early. Common Questions (FAQ) How should I measure 7847709033 inductance under DC bias? Point: Use a calibrated impedance analyzer with a low‑parasitic fixture and apply DC bias with a current source. Evidence: Sweep frequency (100 Hz–1 MHz) and step DC bias from 0 A to rated current in 0.5 A increments, logging L at a standardized test frequency (e.g., 100 kHz). Explanation: Report L vs. I curves and flag samples where L at operating current deviates more than the QA threshold (typically −15%). What temp rise at rated current is acceptable for 7847709033 on my PCB? Point: Acceptable temperature rise depends on board copper and airflow. Evidence: Datasheet typical values and measured samples clustered 28–35°C in our lab; with minimal copper that can be higher. Explanation: Target ≤ datasheet typical +10°C for pass; if higher, increase copper or add thermal vias, or apply current derating to maintain reliability. Which PCB layout changes most reduce EMI and hotspot temperature for 7847709033? Point: Copper and via strategy drive EMI and thermal performance. Evidence: Test boards with solid copper pour and 4–8 thermal vias under pads reduced hotspot temperature by 5–10°C and lowered switching‑node radiated emissions vs. minimal copper. Explanation: Use a split ground plane to control return paths for switching currents, place vias close to pads for heat conduction, and verify with EMI scans and thermal imaging during validation.