Short answer: Two power inductors with the same inductance and similar current numbers are often not comparable, because each maker defines the numbers differently. Before you call a part a substitute, put both datasheets on the same basis for five fields: inductance test condition, Isat drop definition, heating-current temperature rise, temperature rating (ambient or part temperature) and size/land pattern. This guide uses three official datasheets as examples: Bourns SRP1038A, Coilcraft XAL4020 (Document 806) and MAZO VCMA-0420 (revision A4).
1. The five fields, side by side
| Field | Bourns SRP1038A | Coilcraft XAL4020 | MAZO VCMA-0420 |
|---|---|---|---|
| Inductance test | 100 kHz, 1 V | 1 MHz, 0.1 Vrms, 0 Adc | 1 MHz, 1.0 V |
| Isat definition | Inductance drops 20 % | 30 % (typ) inductance drop at 25 °C | L0 drops approximately 30 % |
| Heating current | Irms: 40 °C rise | Irms: 20 °C rise and 40 °C rise columns | Idc: approximately 40 °C rise from 25 °C |
| Temperature rating | –55 °C to +150 °C, temperature rise included | Ambient –40 °C to +125 °C with 40 °C-rise Irms; part max +165 °C | –55 °C to +125 °C, ambient plus self-temperature rise |
| Size | 11.0 × 10.0 × 3.8 mm | 4.0 × 4.0 mm, 2.1 mm max height | 4.75 × 4.45 × 2.0 mm max |
2. Isat: 20 % and 30 % are different numbers for the same core
Saturation current is the DC current at which inductance has fallen by a stated percentage. A 30 % definition is reached at a higher current than a 20 % definition on the same part, so a 30 % Isat looks larger. Worked example already on this forum: SRP1038A-R36M is rated 60 A at a 20 % drop, while the MAZO VCMA-1040-R36-M-1A is 54 A typ at about 30 % ([full comparison](/community/t/11-srp1038a-r36m-bourns-0-36-h-power-inductor-specs-and-mazo)). Those two numbers cannot be ranked against each other. Ask the maker for the L-vs-I curve, or compare at your own peak current on the curves both datasheets print.
3. Heating current: check the ΔT behind the number
Coilcraft prints XAL4020-221ME at 12.0 A for a 20 °C rise and 16.8 A for a 40 °C rise: the same part, two numbers. MAZO and Bourns use a 40 °C rise. Compare 40 °C with 40 °C. All three makers note that rise depends on board copper, airflow and nearby parts, so verify it in the application.
4. Temperature rating: ambient or part temperature?
Bourns and MAZO state a range that already includes self-heating, so the part itself must stay inside it. Coilcraft states an ambient range at the 40 °C-rise current plus a maximum part temperature of 165 °C. A part rated 125 °C including rise, replacing one with a 165 °C part limit, has much less thermal margin at the same ambient.
5. Order of checks
1. Footprint and height: compare land patterns, not just body size. VCMA-0420 is 4.75 × 4.45 × 2.0 mm max against XAL4020 at 4.0 × 4.0 mm, 2.1 mm max height ([full comparison](/community/t/3-can-vcma-0420-r22-m-1a-replace-xal4020-221mec-a-datasheet-co)).
2. Inductance at the same test frequency and voltage.
3. Isat on the same % drop definition, checked against your peak current.
4. Heating current on the same ΔT, then estimated part temperature.
5. Temperature rating: ambient or part temperature.
6. Qualification and logistics: AEC-Q200, MSL, reel size.
A part that passes all six is still a candidate. Interchangeability is confirmed only on your board.
Bourns, Coilcraft and MAZO names and part numbers are used for identification only. MST is not affiliated with or endorsed by these makers.
Original OEM documents (links only)
1. Bourns, SRP1038A Series shielded power inductors datasheet. https://www.bourns.com/docs/Product-Datasheets/SRP1038A.pdf
2. Coilcraft, XAL40xx Series datasheet (Document 806). https://www.coilcraft.com/getmedia/6adcb47d-8b55-416c-976e-1e22e0d2848c/xal4000.pdf
3. MAZO VCMA-0420 datasheet, revision A4. https://store.mst-sg.com/storefront/mazo-datasheets/VCMA-0420/MAZO-VCMA-0420-datasheet-A4.pdf
Request a cross-reference
Send MST your current part number with peak and RMS current, switching frequency, ambient temperature and height limit, and we will return candidates checked field by field. Post a [find-part request](/community/new?kind=part_request) or send a [sourcing RFQ](/services/sourcing-rfq?sourcing_mode=supplier_match). Browse [MAZO power inductors](/store/mazo-power-inductors) in the store.
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