Chip Inductor Power Dissipation: 173 of 5,410 Walsin Rows Imply More Than 10 W Once the Units Are Normalised

You cannot script a chip inductor selector against Walsin’s published export without cleaning it first. We normalised Rated Current and RDC across all 5,410 real rows and computed I²R. 173 rows imply more than 10 W of self-heating. 31 imply more than 1,000 W. The highest is 35,200 W, on a part measuring 1.8 by 1.12 mm.

Venatech Limited, an authorised Walsin distributor in Hong Kong, holds all 203 Walsin Technology (Walsin) parametric export files and 28 Walsin datasheets, 451 pages, none of which covers an inductor. So this post is arithmetic on Walsin_Inductor_ALL.xlsx and nothing else: we reproduced every figure ourselves, the QA row Test123999 is excluded so the denominator is 5,410, and every part number is real. Where the arithmetic does not make physical sense, we say so and ask the question rather than answer it for Walsin.

How many unit conventions does one Walsin inductor column actually carry?

Three, in two different columns, and a fourth column with no unit anywhere. We parsed the unit suffix on every cell of every numeric column in the file. Rated Current is written three ways. RDC is written three ways. Saturation Current is written two ways. SRF(min) carries no unit in its header, in its cells or in any footnote.

The 71 unitless Rated Current rows sit in three series — WLCM (41), WLBD (16) and WLBD(HC) (14) — and the numbers are large. WLBD4532HCU800TH reads 9000 with nothing after it. The 177 unitless RDC rows sit in MCI-TM (172) and WLPN (5); WLPN202012N1R0PB reads 0.07 and MCI0603TM0N6BHBP reads 0.07, while the cell directly above in the same column on another series reads 0.045Ω. We have not seen these three counts published anywhere.

What happens to the dissipation figure once rated current and RDC are normalised?

173 rows exceed 10 W. We restricted the calculation to the 5,162 rows that state an explicit unit on both columns, converted milliamps to amps and milliohms to ohms, and computed I²·RDC — the self-heating a part would see at its own published rated current. 234 rows exceed 1 W. 173 exceed 10 W. 31 exceed 1,000 W. These are surface-mount parts between 1.0 and 6.0 mm long.

The 173 rows are not scattered. They sit in four series: CSME (73), CSMEA (53), WLFI (30) and WQCW (17). That concentration is the useful part of the finding, because it means the question to ask is narrow.

Is the milliamp-to-amp boundary a boundary at all?

No. The obvious assumption is that the file writes milliamps below 1 A and amps above it, so a parser could infer the unit from the magnitude. We tested that assumption against all 5,410 rows and it fails in both directions. 358 rows written in mA exceed 1,000 mA. 397 rows written in A are below 1 A. The lowest amp-stated value is 0.1 A and the highest milliamp-stated value is 6,000 mA, so the two conventions overlap across a 60-fold span.

The overlap is densest exactly where a selector sorts. In the band from 0.9 A to 1.1 A there are 474 part numbers: 203 of them are written in amps and 271 in milliamps. Sort that column as text and you get two interleaved ladders. Sort it as a number with the suffix stripped and 500mA ranks above 3.2A. Inside a single series — WQCW — 500 rows are in milliamps and 69 are in amps.

Which rows will a naive parametric selector rank wrongly?

All 5,410, if the suffix is stripped before sorting, and at minimum the 248 rows with no unit at all. We ran the test. Strip the alphabetic characters and rank Rated Current descending, and the top of the list is not the WQCW and WLFI rows above; it is WLBD4532HCU800TH at a bare 9000, followed by five more WLBD(HC) rows at 6000. Read as milliamps those are 9 A and 6 A parts. Read as amps they are not parts at all.

That last row is the one that costs money, and we have counted it before: only 146 of 5,410 parts publish a saturation current at all, which is the field that decides whether a buck converter survives a load step. The full argument sits in rated current against saturation current.

What does this mean for a cross reference run against this export?

It means the unit map has to be applied before the comparison, not after. Our free cross-reference tool matches against Walsin’s published catalogue and states every difference from your original rather than hiding it — and a stated difference is only worth reading if both sides of it are in the same unit. So we normalise first: milliamps to amps, milliohms to ohms, the 248 unitless cells held back rather than guessed, and the SRF(min) column treated as two scales rather than one, which we counted in self-resonant frequency in Walsin inductors.

Paste up to 500 part numbers or drop your Excel or CSV, filter by commercial or automotive grade, and read the mismatches. Then check what is physically in Hong Kong on ready stock — 1,125 part numbers as at 23 September 2026, a dated snapshot and not a live feed. The full line sits on the Walsin inductor page.

What are we asking Walsin, and what should you ask us?

Four questions, and between them they resolve 248 unitless cells and the 173 rows above. We will publish the answers when they arrive, and we will keep saying they have not arrived until they have.

1. What unit do the 71 blank-suffix Rated Current cells carry, and the 177 blank-suffix RDC cells?
2. Are the CSME and CSMEA DC resistance figures ohms or milliohms? A 1,000x factor sits on that one character.
3. What is the correct rated current unit on the 17 WQCW rows that read tens of amps at 0402 and 0603?
4. What unit is SRF(min) in, per series? The column holds values from 0.015 to 20,000 with nothing to separate them.

What you should ask us is simpler. Send the inductor lines off your bill of materials and we will return the published row for each one with the units expanded and the empty cells marked empty. We hold 28 Walsin datasheets, 451 pages — ask for the one covering your part number and you will get it, or you will get a straight answer that no page covers it, which is the case for all 5,410 inductors today. Hong Kong, Shenzhen, Singapore and Jiangmen, with Chengdu in preparation: Unit 207, 2/F, Sun Ling Plaza, 30 On Kui Street, Fanling, N.T., Hong Kong. (852) 2628 4777.

The short version

Rated Current carries three unit conventions across 5,410 rows — 4,175 in milliamps, 1,164 in amps, 71 with nothing. RDC carries three — 4,892 in ohms, 341 in milliohms, 177 with nothing. The magnitude cannot be used to infer the unit, because 358 milliamp-stated rows exceed 1,000 mA and 397 amp-stated rows are below 1 A. Normalise both columns, compute I²R, and 234 of the 5,162 fully-specified rows exceed 1 W, 173 exceed 10 W and 31 exceed 1,000 W, concentrated in four series. We are not calling that a product defect; we are reporting what the arithmetic returns and asking Walsin which cell to re-read. We hold no inductor datasheet and we say so. Qualification stays with you.

Send us the inductor lines off your bill of materials and we will hand back the normalised row for every one, with the cells we cannot resolve marked unresolved rather than filled in. And a question back: your selector sorted this column last week — did it strip the suffix first, and did anyone check?

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