AMELH6020S-1R2MT Datasheet Analysis: DCR, Isat, Irms
The AMELH6020S-1R2MT datasheet lists three headline numbers—DCR, Isat and Irms—that directly govern copper loss, core margin and thermal reliability in real designs. Correctly interpreting those three figures changes calculated I²R losses, saturation headroom during transients, and the part’s allowable steady-state current; misreading the datasheet DCR or Isat can understate loss by watts and overestimate thermal margin.
This article provides a practical, measurement-aware walkthrough to extract, interpret and apply DCR, Isat and Irms from the AMELH6020S-1R2MT datasheet into power-design choices. The scope covers quick spec extraction, DCR measurement and loss modeling, Isat/Irms interpretation, bench validation methods, and conservative selection rules for switching regulators and point-of-load rails.
Component Overview & Quick Spec Extraction
Key specs to extract from the AMELH6020S-1R2MT datasheet
Point: A compact checklist prevents missed assumptions when selecting the part. Evidence: Pull nominal inductance and tolerance, rated current/Isat, Irms (ΔT spec), DCR typical/max, saturation definition, package and operating temperature from the datasheet. Explanation: These values feed thermal, efficiency and transient simulations; organize them into a single-line spec table for rapid comparison when evaluating alternatives.
| Parameter |
Typical / Max |
Design Notes |
| Nominal Inductance |
1.2 µH ±20% |
Use tolerance for worst-case L in transient sizing |
| DCR |
15 mΩ (Typ) / 20 mΩ (Max) |
Use max DCR for thermal budgets |
| Isat |
20 A (Inductance Drop) |
Understand % L drop at Isat (usually 30%) |
| Irms |
10 A (ΔT spec) |
Thermal-limited rating based on ambient rise |
Why DCR, Isat and Irms are the primary selection metrics
Point: Each metric maps to a different failure or performance domain. Evidence: DCR determines copper loss (affecting efficiency and steady-state heating), Isat defines electrical linearity under peaks (affecting transient droop), and Irms sets thermal steady-state limits. Explanation: For switching converters prioritize low DCR for efficiency at high RMS currents; for high-peak, low-average rails prioritize Isat margin to avoid inductance collapse during transients.
DCR Deep-Dive: Measurement, Interpretation, and Loss Modeling
How DCR is specified and how to measure it
Point: Datasheets list typical and maximum DCR at a reference temperature; measurement technique matters. Evidence: Use a four-wire (Kelvin) resistance measurement at the datasheet reference temperature—usually 25°C—and convert to ohms (mΩ). Explanation: Two-wire LCR readings include lead/contact resistance and can overstate DCR; also account for temperature coefficient (R rises ~0.4%/°C for copper) when comparing bench results to datasheet numbers.
Translating DCR into copper loss and efficiency impact
Point: DCR feeds directly into I²R loss models and efficiency estimates. Evidence: Use P_loss = I_rms² × DCR. Example: with DCR = 20 mΩ and I_rms = 8 A, P_loss = 8² × 0.02 = 1.28 W. Explanation: For switching converters use ripple-current RMS when computing choke loss; if waveform contains DC+AC, compute true RMS. In thermal budgets use typical DCR for nominal estimates and max DCR (plus temp rise) for worst-case heating.
Visualized Power Loss (P = I²R) at 8A RMS
Typical DCR (15mΩ): 0.96W
Isat and Irms: Electrical vs. Thermal Limits
Isat (Saturation Current)
Point: Defined by a specific percentage inductance drop. Evidence: Datasheet states Isat as the DC current at which L falls by X% (e.g., 30%). Explanation: Choose saturation margin—often 20–50% above expected peak currents—to avoid control-loop instability and noise.
Irms (Thermal Rating)
Point: A thermal rating derived from a ΔT rise test. Evidence: Irms references a temperature rise (e.g., 40°C) on a specific board. Explanation: Derate for poor copper or high ambient; reduce Irms by 20–40% in packed assemblies without airflow.
Measurement & Validation Procedures
Bench Validation: DCR & Isat
- •Use Kelvin meter for DCR validation.
- •Sweep DC bias current while measuring inductance.
- •Record the L-drop curve to find the practical saturation point.
Thermal Test: Irms
- •Monitor component temperature with thermocouples.
- •Use thermal camera to see heat distribution on PCB.
- •Replicate worst-case ambient/airflow conditions.
Design Checklist & Application Recommendations
Selection rules for AMELH6020S-1R2MT in common topologies:
For a buck converter use the inductor’s ripple current (ΔI) to compute RMS current and verify DCR loss, ensure Isat > peak current × 1.2–1.5, and verify Irms under steady-state load. Conservative rule: use max DCR in thermal budgets and typical DCR for efficiency targets.
Layout Tip
Maximize copper around the part; add thermal vias under adjacent pours.
Cooling Tip
Place the inductor in the primary airflow path for better Irms performance.
Troubleshooting
Check for audible noise—this often indicates partial saturation during transients.
Summary
Extract the right datasheet numbers, validate them on the bench, and apply conservative derating in design. For the AMELH6020S-1R2MT capture nominal/max DCR, Isat definition and Irms ΔT test conditions, then use four-wire DCR checks, L vs. DC bias sweeps, and thermal runs to produce usable derating curves. Closing note: always include DCR in both efficiency and thermal calculations.
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✓
Extract DCR (typ/max), Isat and Irms from the datasheet for direct loss and thermal modeling.
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✓
Compute copper loss using P = I_rms² × DCR; use max DCR for thermal reliability.
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✓
Validate Isat by L vs. DC bias sweeps and confirm Irms with local PCB thermal ramp tests.
Frequently Asked Questions
How should I measure DCR for an inductor used in a buck converter?
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Measure with a four-wire (Kelvin) ohmmeter at the datasheet reference temperature and fixture identical to the application. Eliminate lead and contact resistance, record at baseline temperature, and account for copper temperature coefficient when converting to on-board operating conditions.
How much saturation margin should I leave relative to peak current?
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A practical rule is 20–50% headroom above expected peak current depending on transient severity and duty cycle. For high transient systems prefer larger margins; for well-filtered, low-peak systems use the lower end of the range while validating with L vs. DC bias sweeps.
What’s the best way to produce an Irms derating curve for a specific PCB?
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Perform thermal ramp tests: apply increasing steady current, measure ΔT on the part and adjacent copper, and repeat at different ambient temperatures and airflow conditions. Plot current vs. allowable ambient for your target ΔT to produce a conservative derating curve for design use.
