The AMELH6060S-180MT is assessed here with a concise data-driven hook: typical datasheet figures indicate an 18 μH nominal inductance with saturation current and thermal rise that generally govern usable continuous RMS current. For design decisions, the key limit is keeping continuous RMS current below the thermally-derived allowable current to avoid excessive ΔT and loss.
This report synthesizes datasheet-sourced electrical figures, expected measured behaviors (saturation, DCR, thermal), and practical test recipes so designers can establish actionable continuous-current limits, create derating curves, and reproduce benchmark numbers on the bench with standard instruments.
Series & Part Background (Background introduction)
Part identification & nominal specs
Point: Part identity and nominal values matter for selection. Evidence: The part number corresponds to a molded-power family in a 60×60 footprint, nominal inductance 18 μH. Explanation: Typical datasheet ranges we'll use for guidance: tolerance ±20%, DCR approximately 0.05–0.35 Ω, Isat in the mid-single to low-double ampere range and Irms lower than Isat; ΔT spec often ~40°C at rated Irms.
Parameter
Nominal / Typical
Inductance (L)
18 μH
Tolerance
±20%
DCR
~0.05–0.35 Ω
Isat (datasheet)
~6–12 A (typical spec range)
Irms (rated)
~4–8 A (thermal-limited)
ΔT @ Irated
~40°C (typical)
Typical applications and performance envelope
Point: Typical uses guide acceptable limits. Evidence: This molded choke suits power conversion chokes, LC input filters, and EMI suppression where moderate currents and compact footprint are required. Explanation: Expect this 18 μH device to appear in 100 kHz–1 MHz switching contexts for 5–12 V rails; tradeoffs prioritize inductance and size at the expense of higher DCR and lower continuous current relative to larger cores—search for an 18uH choke for DC-DC converter when low ripple and modest current are needed.
Electrical Limits: Inductance, DCR, and Saturation (Data analysis)
Inductance tolerance and measurement conditions
Point: L is frequency- and bias-dependent. Evidence: Datasheet L is specified at a test frequency (commonly 100 kHz or 1 MHz) without DC bias; measured L typically falls with increasing test frequency and under DC bias. Explanation: Report L vs. frequency and L vs. DC bias: e.g., measure at 100 kHz and 1 MHz, and with DC bias steps to quantify usable inductance under operating current for accurate ripple and loop calculations for the 18uH inductor.
DCR, saturation current (Isat), and test definitions
Point: DCR and saturation define loss and peak capability. Evidence: DCR is measured at 20–25°C with four-wire technique; Isat is reported as current where L drops to a specified percent (commonly 70%–80%). Explanation: Expect DCR in the table range—thermal rise from copper loss limits continuous Irms. Use datasheet Isat as a peak-limit reference but rely on thermally-derated Irms for continuous operation; copper loss = I²·DCR and rises with temperature.
Thermal Behavior & Current Derating (Data analysis)
Current Limit Comparison (Visualization)
RMS Current:
4-8A (Thermal Limit)
Sat Current:
6-12A (Magnetic Limit)
*Note: Thermal limits (Irms) are typically the primary constraint for continuous operation.
Temperature rise, thermal limits, and ambient considerations
Point: ΔT at rated current determines continuous allowance. Evidence: Datasheet ΔT is usually specified at the rated Irms into free-air ambient; maximum winding/component temperature determines safe operating point. Explanation: To translate ΔT into allowed continuous current, compute winding temperature = ambient + ΔT; ensure that winding temp stays below the max operating temperature. Example formula: I_allowed ≈ Irated × sqrt((ΔT_spec)/(ΔT_measured_at_I)).
Derating curves and practical current limits
Point: Combine thermal and saturation to build derating. Evidence: Practical derating curves plot allowed continuous current vs. ambient; they fold in I²·DCR heating and any core temperature limits. Explanation: Construct a curve using measured DCR, estimated core loss at switching frequency, and ΔT spec. Provide recommended continuous currents by ambient (25°C, 50°C, 70°C) and limit peaks by Isat and short-duration thermal capacity.
Measurement & Test Methodology (Methods guide)
Test setup to reproduce datasheet numbers
Point: Reproducible setup prevents measurement error. Evidence: Use an LCR meter with defined test frequency (100 kHz/1 MHz), four-wire DCR meter for low-ohm readings, and DC bias source for Isat tests; thermocouple on winding for ΔT. Explanation: Fixture recommendations: short Kelvin leads, minimize loop area, allow thermal stabilization before reading. Expect tolerance windows: L ± tolerance, DCR ±5% at 25°C; document instrument settings.
Saturation test and thermal soak procedure
Point: Safe saturation and thermal tests require incremental steps. Evidence: Increment DC bias in steps while logging L; stop when L reaches datasheet-defined drop. For thermal soak, apply continuous current, log ΔT until steady state (typically 10–30 minutes). Explanation: Incremental DC steps of 0.5–1 A with 10–30 s settling let you detect magnetic compression without overheating. Thermal soak logging at 30–60 s intervals until stable gives repeatable ΔT values for derating.
Example Limits in Two Real-World Circuits (Case studies)
Example A — Buck converter choke
Point: Use-case calculation for buck choke. Evidence: For a synchronous buck with 6 A peak and 4 A continuous, estimate copper loss using DCR and switching-core loss via frequency harmonics. Explanation: With DCR = 0.1 Ω, I²·DCR at 4 A yields 1.6 W; if ΔT at rated Irms is specified as 40°C, a 25°C ambient yields winding ~65°C—acceptable if max rating is higher. Add 20–30% safety margin for long-term reliability.
Example B — LC input filter
Point: Continuous RMS heating dominates input filter use. Evidence: In an input filter, the inductor sees near-continuous RMS current; ripple current adds modest extra heating. Explanation: If RMS current approaches rated Irms, limit operation by thermal derating or increase airflow. Layout recommendations: maximize copper area and thermal vias, separate close-placed heat sources, and keep the choke clear of hot components to reduce cumulative ΔT and EMI coupling.
Point: Prioritize mitigations by impact and cost. Evidence: Effective mitigations include parallel inductors, forced airflow, larger footprint or lower-DCR variants. Explanation: Prioritize forced airflow and layout improvements first (low cost), then parallel devices or alternate parts (higher cost). Document changes and re-run the measurement recipe to validate new limits.
FAQ
What is the practical continuous current limit for AMELH6060S-180MT in a closed chassis?
Practical continuous current depends on ambient and airflow. Use measured DCR and ΔT to derive allowed Irms: for example, if datasheet ΔT is 40°C at Irated, in a 40°C ambient you must ensure winding temp (ambient + ΔT) stays below max rating—apply 20–30% derating for closed-chassis operation.
How should one test AMELH6060S-180MT for saturation current reproducibly?
Use an LCR meter to monitor inductance while applying incremental DC bias with a stable current source. Increase current in 0.5–1 A steps, allow settling, and log L; the saturation point is where L drops to the datasheet-specified percentage. Keep thermal effects minimal by limiting dwell time during the sweep.
What layout and cooling tips best mitigate 18uH inductor heating?
Place the inductor away from other heat sources, provide thermal vias under nearby copper, maximize copper pour for heat spreading, and add forced convection if possible. If PCB real estate allows, choose larger footprint or parallel inductors to reduce per-part I²·R heating and lower steady-state ΔT.
