1812-222F

FAQFrequently Asked Questions

• Can the API Delevan 1812-222F inductor handle 535 mA continuous current in a switching power supply design, or will thermal effects reduce its effective current rating? The 1812-222F is rated for 535 mA continuous current, but thermal behavior depends on board layout and ambient conditions. With 700mOhm maximum DC resistance, a 535 mA load dissipates approximately 200 mW in the inductor itself. In a confined layout without adequate copper area for heat spreading, localized temperature rise can occur, potentially reducing the Q factor and increasing core losses at the 7.9 MHz test frequency. For designs operating near the 535 mA limit in high-ambient environments (above 85°C), verify thermal margin using thermal imaging or FEA analysis, or derate the current by 10–15% to maintain reliability margins.
• How does the 700mOhm DCR of the 1812-222F compare to alternative 2.2 µH inductors in the same package, and when should I specify a lower-DCR part? The 700mOhm DCR is typical for unshielded ferrite inductors in the 1812 package at this inductance value. Competitors such as the Murata LQM18FN2R2D00 offer similar DCR (~650–750mOhm), while some shielded alternatives (e.g., TDK SPM6530T-2R2M) may have slightly lower DCR but with trade-offs in size or cost. Choose lower-DCR parts only if efficiency analysis shows resistive losses are a primary power budget constraint; for most sub-1 A switching applications, the 1812-222F's DCR is acceptable. Lower DCR typically increases cost and may require a larger package.
• The 1812-222F is unshielded—what are the practical implications for board layout in a mixed-signal design with high-speed digital circuits nearby? Unshielded inductors radiate magnetic fields, which can couple into sensitive analog or high-speed digital traces if placed too close. For the 1812-222F, maintain at least 0.2 inches (5 mm) clearance from clock lines, data buses, and high-impedance analog nodes. In densely packed layouts, route return paths directly beneath the inductor to minimize loop area and radiated field. If coupling to adjacent circuits cannot be avoided, consider a shielded alternative (which adds ~0.05" height and cost), or perform pre-layout EMI simulation. The 700mOhm DCR and ferrite core generate harmonic content up to the 55 MHz self-resonant frequency, so pay particular attention to circuits sensitive to frequencies above 10 MHz.
• Can the 1812-222F be used as a replacement for a competing 2.2 µH inductor, and what design parameters should I verify before swapping part numbers? Direct mechanical and electrical replacement is possible if the competing part also uses the 1812 (3.2 mm × 3.2 mm) package and has a 535 mA current rating or higher. Before substitution, compare: (1) DC resistance—if the alternate part has significantly lower DCR (<600mOhm), efficiency may improve but cost will likely increase; (2) self-resonant frequency—the 1812-222F's 55 MHz SRF is adequate for most applications below 20 MHz, but verify the alternate part's SRF if operating near or above 30 MHz; (3) saturation behavior—if the datasheet provides saturation current (Isat), confirm it exceeds your worst-case transient current by at least 20%; (4) temperature coefficient—ferrite inductors from different manufacturers exhibit different inductance drift with temperature, so re-characterize inductance across your operating range (-55°C to 125°C for the 1812-222F) if the replacement part's temperature characteristic is unknown.
• Is the API Delevan 1812-222F suitable for RF or high-frequency filtering applications, or is it limited to low-frequency power supply use? The 1812-222F is primarily intended for power supply filtering and switching applications below ~20 MHz. While it has a measured Q of 50 at 7.9 MHz and a 55 MHz self-resonant frequency, these parameters are moderate for RF applications. For RF or precision filtering above 30 MHz, dedicated RF inductors with higher Q (typically 80–120 at operating frequency) and more stable frequency response are preferred. The 700mOhm DCR and ferrite core also exhibit higher insertion loss at higher frequencies, making the 1812-222F inefficient for low-loss RF matching or tuning networks. Use the 1812-222F for DC-link filtering, output LC filters in switching converters, and EMI suppression up to ~15 MHz; for higher-frequency applications, consult RF-specific inductor families.
• What is the saturation behavior of the 1812-222F, and how should I handle inrush or transient currents during power-on or fault conditions? The 1812-222F datasheet does not explicitly specify saturation current (Isat); however, ferrite-core inductors of this size and inductance typically saturate between 800 mA and 1.2 A depending on core material and bias point. During power-on inrush or short-circuit transients, the inductor's inductance collapses if current exceeds saturation, reducing filtering effectiveness and potentially allowing damaging current spikes. To protect against saturation: (1) design the input current-limiting circuit or soft-start to limit inrush to <700 mA (below the rated 535 mA with margin); (2) if higher transient tolerance is required, select an inductor with specified Isat >1.5 A or increase the inductance value; (3) use a series current-sense resistor or active current-limiting IC to clamp fault currents; (4) for safety-critical applications, contact API Delevan for saturation data or select an inductor from a series with published Isat ratings.
• The 1812-222F operates from –55°C to 125°C—what happens to inductance and Q factor at temperature extremes, and how should I adjust circuit tuning or filter cutoff frequencies? Ferrite inductors experience inductance drift with temperature, typically ranging from –5% to +10% across the full –55°C to 125°C operating range, depending on the ferrite mix and core construction. The 1812-222F's DC resistance also increases approximately 0.4%/°C due to copper resistivity. At 125°C, DCR may increase to ~750–800mOhm from the 25°C baseline of 700mOhm. The Q factor degrades at temperature extremes due to increased losses. For applications requiring tight frequency control (e.g., resonant power supplies or phase-locked loop filters), characterize the actual inductance and Q across your operating temperature range using an impedance analyzer at the circuit's operating frequency (not just the 7.9 MHz test frequency). If the application requires <2% inductance tolerance across temperature, either select a part with tighter temperature specifications (contact the manufacturer), use active tuning, or derate the design margin.
• How does the ±1% inductance tolerance of the 1812-222F affect filter cutoff frequency or resonant frequency in a tuned LC circuit, and when should I specify tighter tolerance? The ±1% inductance tolerance, combined with typical capacitor tolerances (±5% to ±10%), results in overall LC resonant frequency tolerance of ±3% to ±6%, depending on whether L and C tolerances are correlated. For a nominal 2.2 µH and standard ceramic capacitor, this translates to ±0.066 MHz to ±0.132 MHz shift around a 1 MHz cutoff frequency. For most switching power supplies and EMI filters, ±6% frequency drift is acceptable because the filter operates over a wide bandwidth. However, if the application requires a precise resonant peak (e.g., wireless power, tuned matching networks, or phase-locked filters), use hand-matched L-C pairs or select inductors with tighter tolerance (±0.5%), which may require special ordering and add cost. Alternatively, use an adjustable capacitor (trimmer) to compensate for inductance variation.
• The 1812-222F is RoHS non-compliant and has MSL 1—what are the implications for supply chain, storage, and end-product certification? RoHS non-compliance typically indicates the part contains lead solder or lead-based materials, limiting use in consumer electronics destined for the EU, but acceptable for industrial, automotive, medical, and aerospace applications with exemptions. Verify that your end-product's regulatory classification (e.g., industrial equipment, automotive tier-2 component) allows non-RoHS parts; many automotive OEMs now require RoHS compliance even for exempted categories. MSL 1 (unlimited moisture sensitivity) is favorable—it means the 1812-222F can be stored indefinitely without special desiccation, simplifying warehouse management and reducing bake-out requirements. However, cross-check with your supply chain and procurement policies; if your end-product requires RoHS compliance, contact the manufacturer for RoHS-compliant alternatives, which may exist in similar packages.
• Should I use the 1812-222F for critical power supply designs where inductor failure could cause cascading system failure, or are there reliability concerns specific to this part? The 1812-222F, like all ferrite inductors, can fail via core cracking (thermal stress, mechanical shock), or open winding (solder joint fatigue, corrosion). API Delevan is an established manufacturer, and the 1812 series has been in production for decades, so field reliability data is generally favorable. However, for mission-critical applications (aviation, medical devices, autonomous systems), implement fault tolerance: (1) use redundant inductors in parallel to provide graceful degradation if one opens; (2) add monitoring circuits (current sensors or voltage comparators) to detect inductor faults; (3) design the circuit so inductor failure does not directly damage downstream components (e.g., clamp flyback voltages with Schottky diodes); (4) specify conformal coating if operating in high-humidity or corrosive environments; (5) perform thermal cycling tests (-55°C to 125°C, minimum 10 cycles) on prototypes to identify solder joint fatigue before production. For do-not-fail applications, consult military-grade inductor suppliers (e.g., Vishay IHLP, TDK SPM) with higher screening and documentation.
• In a multi-layer PCB design, how should I route the copper planes and traces around the 1812-222F to minimize coupling to nearby components and maintain signal integrity? The 1812-222F's 3.2 mm footprint occupies minimal board area, but its magnetic field extends several millimeters beyond the component. Optimal layout: (1) place the inductor away from high-speed signal traces and clocks; (2) route return paths directly beneath and adjacent to the inductor to form a tight magnetic loop, confining the field; (3) if possible, use a solid ground plane immediately below the inductor layer to absorb stray fields; (4) maintain >0.2" clearance from sensitive analog traces (ADC inputs, reference voltage lines); (5) if the inductor is on an inner layer, flood-fill the surrounding area with ground stitching vias every 0.1 inches to suppress radiated fields; (6) avoid routing high-speed differential pairs parallel to the inductor; instead, cross over it perpendicularly if routing must be proximate. For high-speed designs (>50 MHz clock), perform pre-layout EMI simulation or time-domain reflectometry (TDR) analysis to verify signal integrity near the inductor.
• Can the 1812-222F be soldered using standard lead-free (Pb-free) reflow processes, and are there specific temperature or dwell time constraints? The 1812-222F is typically solderable with standard lead-free SAC305 (Sn/Ag/Cu) solder at reflow temperatures of 245–260°C peak. API Delevan publishes reflow profiles for their inductors; verify the specific profile in the application note or contact the manufacturer. Lead-free solder has a higher melting point than lead-tin, so reflow ovens must reach the specified temperature ramp rates and dwell times—typically 30–60 seconds at peak temperature for the 1812 package. Potential concerns: (1) excessive reflow temperature (>265°C for extended periods) can degrade ferrite core material, increasing losses; (2) lead-free solder is more prone to whisker growth if current flows through solder joints at elevated temperatures, so use conformal coating if operating in high-current, high-temperature environments; (3) hand-soldering the 1812-222F is difficult due to its small size; use a reflow oven or hot-air station with temperature profiling to ensure reliable joints. If rework is required, limit reflow cycles to <3 times to minimize thermal stress.
• What is the frequency response (impedance vs. frequency) of the 1812-222F, and how does it behave as an LC resonance develops with parasitic capacitance? The 1812-222F exhibits inductive behavior from DC up to its self-resonant frequency (SRF) of 55 MHz. Below ~5 MHz, impedance is dominated by inductance (Z ≈ ωL), and Q remains relatively high (~50 at 7.9 MHz). As frequency approaches the SRF (55 MHz), parasitic capacitance between windings begins to resonate with inductance, and impedance peaks sharply near resonance before dropping. Beyond 55 MHz, the inductor behaves as a capacitor due to parasitic effects. For practical design: (1) do not use the 1812-222F at frequencies approaching or exceeding 50 MHz; (2) if your filter or matching network operates at 30–50 MHz, request frequency-dependent impedance data (Z vs. f curve) from the manufacturer or measure it with a network analyzer; (3) the Q of 50 @ 7.9 MHz will degrade at higher frequencies, reducing filter attenuation; (4) account for parasitic capacitance in resonant circuits by adding a small tuning capacitor or performing SPICE simulation with frequency-dependent models.
• Is the 1812-222F suitable for use in a high-current DC-DC converter's output filter, or should I parallel multiple inductors for higher saturation margin? A single 1812-222F is acceptable for converters delivering <500 mA at the 2.2 µH inductance value, assuming the converter's switching frequency is >500 kHz and the output filter design provides adequate ripple current margin. However, if your converter operates at <500 kHz (slower switching), or if transient load steps regularly exceed 700 mA, paralleling two or more 1812-222F inductors is advisable to: (1) increase effective saturation current (two 1812-222F in parallel nominally support ~1 A); (2) distribute current more evenly, reducing hotspot temperature; (3) provide redundancy—if one inductor saturates or fails open, the other continues operation. When paralleling, use identical part numbers and layout symmetrically to ensure current sharing. Note that paralleling two 1812-222F reduces inductance to ~1.1 µH and requires careful PCB layout to avoid coupling between the two inductors, which would counteract the parallel effect.
• How should I account for the 1812-222F's DC resistance in efficiency calculations for a switching power supply, and at what point does DCR become the limiting factor? The 1812-222F's 700mOhm DCR contributes resistive loss of P = I²R; at 535 mA, this equals approximately 0.2 W. In a 5 V / 2 A converter (10 W total output), the inductor loss is 2%, which is often negligible compared to switching losses and other passive components. However, in low-voltage, high-current applications (e.g., 1 V / 10 A = 10 W), the same 0.2 W represents 2% efficiency loss—still manageable. Where DCR becomes limiting: (1) in very high-efficiency designs targeting >95% efficiency, each 0.1 W of loss matters; (2) in battery-powered applications where extended runtime depends on minimizing standby losses; (3) when the converter operates at very high duty cycles (>90%), where inductor conduction time is long. If DCR loss exceeds your efficiency budget, either parallel multiple inductors (reduces DCR proportionally) or select a lower-DCR inductor, typically at the cost of larger package size or higher price. For most conventional 5 V / 3.3 V supplies at moderate current (0.5–2 A), the 1812-222F's DCR is not a limiting factor.
• Can the 1812-222F be used in resonant or soft-switching topologies, and how does the Q factor of 50 affect circuit efficiency compared to higher-Q inductors? Resonant and soft-switching topologies (LLC, series-resonant, parallel-resonant) rely on LC tank circuits to resonate at the switching frequency, allowing zero-voltage or zero-current switching to reduce losses. A Q factor of 50 @ 7.9 MHz is moderate for resonant circuits; higher Q (70–120) reduces resistive losses and narrows the resonant peak, improving efficiency. The 1812-222F's Q of 50 is adequate for resonant supplies operating at 1–5 MHz with moderate efficiency requirements (>85%). However, if your design targets >90% efficiency in a resonant topology, consider higher-Q inductors (e.g., TDK SPM series with Q >70), which offer lower losses but at higher cost and often in larger packages. Practically, simulate the resonant circuit using the 1812-222F's measured Q to verify that switching losses and tank losses remain within budget. If simulation shows efficiency shortfall due to Q, then upgrade to a higher-Q part; otherwise, the 1812-222F is cost-effective.
• In a noise-sensitive application like audio or precision instrumentation, how does the unshielded 1812-222F compare to shielded inductors, and when is shielding necessary? Unshielded inductors radiate magnetic flux, which can couple inductively into nearby audio traces, ADC inputs, or high-impedance nodes, introducing audible noise or measurement errors. Shielded inductors (e.g., TDK SPM series) confine flux within a metal shell, reducing radiated coupling by 10–20 dB depending on shield design. For audio applications with dynamic range >90 dB, shielded inductors are recommended, especially if the power supply inductor is located near analog signal processing stages. For precision instrumentation (16-bit or higher ADCs), shielding also helps reduce coupling from switching-frequency harmonics. Trade-offs: shielded inductors are typically 0.05–0.1 inches taller, increase PCB layer complexity, and cost 20–50% more. If your application includes adequate filtering (ferrite beads, LC networks) between the inductor and sensitive circuits, and layout spacing is >0.3 inches, the 1812-222F's unshielded design may be acceptable. If coupling is a concern, measure EMI with an unshielded prototype; if noise margins are marginal, switch to a shielded variant.
• What precautions should I take when desoldering or reworking the 1812-222F during prototyping or repair? The 1812-222F's compact size (3.2 mm × 3.2 mm) and ferrite core material present specific rework challenges. During desoldering: (1) use a hot-air station set to 300–320°C (higher than reflow peak to compensate for rapid cooling); (2) apply heat for 15–20 seconds to ensure solder fully liquefies; (3) avoid prolonged heating (>30 seconds), which degrades ferrite and stresses solder joints; (4) use a suction tool or solder wick to remove excess solder; (5) do not use a soldering iron directly on component leads, as this concentrates heat and risks cracking the ferrite core. When reinstalling: (1) clean flux residue with IPA and a brush to prevent corrosion; (2) apply fresh solder paste and reflow using the same profile as initial assembly; (3) if reworking more than twice, inspect the component under a microscope for hairline cracks in the ferrite. For production volumes, minimize rework by employing X-ray inspection and automated optical inspection (AOI) post-reflow to catch defects early.
• How does the 1812-222F perform in automotive or harsh industrial environments, and are there additional derating or qualification requirements? The 1812-222F's –55°C to 125°C operating range covers most automotive and industrial applications. However, automotive environments introduce additional stresses: (1) thermal cycling from –40°C to +125°C during engine shutdown/startup cycles can cause repeated stress on solder joints, leading to fatigue; (2) vibration from engine and road can induce mechanical stress on the component; (3) high humidity and salt spray (coastal regions, de-icing environments) accelerate corrosion if conformal coating is not used. For automotive qualification: apply conformal coating (acrylic or urethane) to protect against corrosion; perform extended thermal cycling (-40°C to +125°C, minimum 15 cycles) and vibration testing per IEC 60068-2-6 (sinusoidal vibration, 1–500 Hz) as part of design validation. Also verify that the 1812-222F's RoHS non-compliance aligns with your OEM's automotive standards (many now require RoHS for Tier-1 components). For harsh industrial environments (foundries, chemical plants), add potting compound around the inductor to prevent moisture ingress and provide mechanical damping against vibration.
• For a PCB assembly house unfamiliar with the 1812-222F, what key information should be provided in the design documentation and bill of materials to ensure correct placement and soldering? Include the following in your design documentation: (1) part number: API Delevan 1812-222F, with a link to the official datasheet; (2) package specification: 1812 (3.2 mm × 3.2 mm), 2-pad SMD with solder pads on the ends (not on sides); (3) reflow profile: use standard lead-free SAC305 profile (245–260°C peak, 30–60 sec dwell) per IPC-A-610 guidelines; (4) placement notes: orient component so pads align with PCB trace routing (correct polarity is not typically critical for inductors, but ensure consistent orientation for visual inspection); (5) solder paste recommendations: use type-3 or type-4 solder paste (particle size 20–38 µm) to avoid bridging on the 3.2 mm pads; (6) inspection criteria: after reflow, verify solder fillets on both ends are smooth and shiny with no voids >50% of fillet volume; (7) rework allowance: specify maximum two reflow cycles to preserve ferrite core integrity. Provide a high-resolution assembly drawing with reference designators, fiducials, and clearance zones marked.