Inductor DCR vs inductance is not monotonic in Walsin’s export. We walked 2,086 adjacent inductance steps across 92 sub-families: DCR rises on 1,348, holds on 544 and falls on 194. At those 194 steps every part at the larger inductance publishes a lower DCR than every part at the smaller one. A Hungarian engineer who sorts by DCR will mis-rank 9.3 percent of steps.
A design engineer in Hungary assumes that more turns means more copper means more resistance. We checked that assumption against the data instead of arguing it. Venatech Limited, an authorised Walsin distributor in Hong Kong, holds the inductor parametric export published by Walsin Technology (Walsin): 5,411 rows, of which Test123999 is a QA test row we exclude, leaving 5,410. This post is written from the Inductance, Unit and RDC columns of that file. We hold no Walsin inductor datasheet, so every figure is the export’s, and every part number below is real.
Does DCR always rise when inductance rises within one Walsin series?
No. We parsed all 5,410 rows and kept the 4,552 that sit in a sub-family with at least two inductance values, an explicit ohm or milliohm suffix on RDC, and a real inductance. A sub-family is series, case size, the two-character construction code after the size, and thickness: 92 of them. Inside them there are 2,086 adjacent inductance steps. DCR rises on 1,348 (64.6 percent), is identical on 544 (26.1 percent) and falls on 194 (9.3 percent). We counted a fall only when every part at the larger inductance is below every part at the smaller one, so a tie-break between tolerance variants cannot create one.
| Outcome at an adjacent inductance step | Steps | Share | Match / mismatch against “DCR never falls as inductance rises” |
|---|---|---|---|
| DCR higher at the larger inductance | 1,348 | 64.6% | Match |
| DCR identical at both inductances | 544 | 26.1% | Match on the rule, mismatch on discrimination: the column cannot rank the pair |
| DCR lower at the larger inductance | 194 | 9.3% | Mismatch |
| Total steps | 2,086 | 100% | 92 sub-families |
We have not seen this counted anywhere. 31 of the 92 sub-families contain at least one falling step; 61 do not.
Which Walsin inductor series break the rule, and how often?
Nine of the 27 series that have testable steps, mostly signal-class multilayer and wirewound ranges. WLCW has 53 falling steps out of 331 (16.0 percent), WLFW/WFI 15 of 94 (16.0 percent), WCA and WCI 38 of 257 each (14.8 percent) and WQCW 35 of 239 (14.6 percent). The power-class ranges show none: AIP, MIP, WIP, WPA, WLPH and VEFL have 0 falls across their steps.
| Series | Steps tested | Falling steps | Share | Match / mismatch against a monotonic DCR ladder |
|---|---|---|---|---|
| WLCW | 331 | 53 | 16.0% | Mismatch |
| WLFW/WFI | 94 | 15 | 16.0% | Mismatch |
| WCA | 257 | 38 | 14.8% | Mismatch |
| WCI | 257 | 38 | 14.8% | Mismatch |
| WQCW | 239 | 35 | 14.6% | Mismatch |
| WLFI | 41 | 3 | 7.3% | Mismatch |
| CSME | 59 | 4 | 6.8% | Mismatch |
| MCI | 237 | 4 | 1.7% | Mismatch, but rare |
| WLCM | 242 | 4 | 1.7% | Mismatch, but rare |
| AIP, MIP, WIP, WPA, WLPH and 13 more | 329 | 0 | 0.0% | Match |
The practical reading: the further a series is from a bulk-wound power inductor, the less its DCR column behaves like a ladder. For the construction question behind that, see multilayer vs wirewound chip inductors.
How big are the drops when the bigger inductor has the lower DCR?
Often large. We computed the fall at each of the 194 steps as the highest DCR at the larger inductance against the lowest at the smaller. The median fall is 16.7 percent, 65 steps fall by 25 percent or more and 17 fall by 50 percent or more. The largest is 86.7 percent. These are not rounding artefacts.
| Step (smaller inductance to larger) | DCR as published | Rated current as published | Your incumbent part | Match / mismatch |
|---|---|---|---|---|
WLCW1608HQJ2N2PB 2.2 nH to WLCW1608HQJ3N3PB 3.3 nH |
0.18 ohm to 0.024 ohm | 900 mA to 1.9 A | Mismatch: inductance up 50 percent, DCR down 86.7 percent | |
WLCW2012Z0J2N2PB 2.2 nH to WLCW2012Z0J2N7PB 2.7 nH |
0.08 ohm to 0.03 ohm | 600 mA to 600 mA | Mismatch: DCR down 62.5 percent, current unchanged | |
WFI2520FSR20J 0.20 uH to WFI2520FSR24J 0.24 uH |
0.285 ohm to 0.135 ohm | 700 mA to 700 mA | Mismatch: DCR down 52.6 percent, current unchanged | |
WLFI1608Z0MR82TB 0.82 uH to WLFI1608Z0M1R0TB 1.0 uH |
2.1 ohm to 0.6 ohm | 35 A to 25 A | Mismatch: DCR down 71.4 percent | |
MCI0603TN20NHHBP 20 nH to MCI0603TN22NHHBP 22 nH |
2.3 ohm to 1.9 ohm | 150 mA to 150 mA | Mismatch: DCR down 17.4 percent | |
WLCW4532Z0KR18PB 180 nH to WLCW4532Z0KR22PB 220 nH |
110 mohm to 105 mohm | 1.15 A to 940 mA | Mismatch: DCR down 4.5 percent and rated current also down |
The last row is the useful one. DCR fell and rated current fell with it, which cannot both be explained by a single copper path. Whether those cells are measurement spread, a change of winding or a transcription error is a question for Walsin; the export does not say.
What happens to rated current at those 194 steps?
It does not follow DCR. We compared Rated Current at the 194 steps, using only cells with an explicit unit. Rated current is strictly higher at the larger inductance on 52 steps, strictly lower on 36, and neither strictly higher nor strictly lower on 106. A lower DCR with a higher current is the story an engineer expects; it covers 52 of the 194, about a quarter.
The 36 steps where both fall deserve a manual check against the source datasheet before the part reaches a thermal review. For how DCR and rated current relate when the data is clean, see reading RDC and DC resistance.
Why are the 194 not 194 independent findings?
Because Walsin repeats data across series. WCA and WCI have identical counts (257 steps, 38 falls) since sister series publish the same row under a different prefix. Collapsing steps with the same case size, thickness, inductance pair and DCR values leaves 85 distinct falls out of 980 distinct steps. We published the wider effect, 3,146 of 5,410 part numbers carrying data identical to another series, in chip inductor second source. The honest headline is therefore 194 as the export presents them and 85 as physical ladders. Either way it is not zero.
Two exclusions are worth stating. We dropped six rows whose inductance cell disagrees with the code in the part number or carries the wrong unit (WIP322512A-1R5ML, WIP322512A-3R3ML, WLPH201610MR47PP, WIP201610P-R47ML, WQPH201610M1R5PS, WPA201610S-1R5ML), because they would have created false falls. And the 71 inductors with a unitless Rated Current are used for DCR only.
What should a Hungarian design engineer do with a DCR sort?
Sort by DCR to shortlist, never to rank: 194 of 2,086 steps in the file break the ladder, and 544 more carry no ranking information. Three rules follow from those counts.
- Do not assume the bigger inductor in a series is the higher-loss part. At 194 steps in the export it is not.
- Treat 544 ties as no information. Where DCR is identical at two inductances, the column cannot choose between them.
- Re-derive loss from the datasheet value for your exact part number. We hold 28 Walsin datasheets, 451 pages, and none covers an inductor; request the Walsin inductor sheet for your part from Walsin and compare it with the export.
Our free cross-reference tool shows the published DCR beside the original and states differences instead of ticking a box. What is in Hong Kong is on ready stock: 1,125 part numbers as at 23 September 2026, a dated snapshot and not a live feed. The range sits on the inductor page.
The short version
We walked 2,086 adjacent inductance steps in 92 sub-families of Walsin’s inductor export. DCR rises on 1,348, ties on 544 and falls on 194, 9.3 percent. The falls sit in nine series, led by WLCW with 53 of 331 and WLFW/WFI with 15 of 94; the power-class series have none. The median fall is 16.7 percent and the largest is 86.7 percent, at WLCW1608HQJ2N2PB to WLCW1608HQJ3N3PB. Collapsing mirrored series leaves 85 distinct falls. We will not tell you a part matches on DCR. We will show you the cell the file holds. Confirm against both datasheets and qualify in your own circuit.
Send us the inductor line off your BOM with the DCR you designed to, and we will tell you which neighbouring inductances in Walsin’s file sit lower. And a question back: when your selector sorted by DCR, did you assume the sort was a ladder?
Frequently asked questions
Does inductor DCR always increase with inductance in Walsin’s data?
No. Across 2,086 adjacent inductance steps in 92 sub-families, DCR rises on 1,348, is identical on 544 and falls on 194, which is 9.3 percent. A fall means every part at the larger inductance publishes a lower DCR than every part at the smaller one.
Which Walsin inductor series have a falling DCR as inductance rises?
Nine: WLCW with 53 falling steps, WCA and WCI with 38 each, WQCW with 35, WLFW/WFI with 15, CSME with 4, MCI with 4, WLCM with 4 and WLFI with 3. Power-class series such as AIP, MIP, WIP and WPA show none.
How large is the biggest DCR drop between neighbouring inductances?
86.7 percent. WLCW1608HQJ2N2PB at 2.2 nH publishes 0.18 ohm and WLCW1608HQJ3N3PB at 3.3 nH publishes 0.024 ohm. The median drop across all 194 falling steps is 16.7 percent, and 17 steps fall by half or more.
Does rated current rise when DCR falls at those steps?
Not reliably. Rated current is strictly higher on 52 of the 194 falling steps, strictly lower on 36 and neither on 106. The 36 where both DCR and current fall should be checked against the datasheet.
Are the 194 falling steps all different parts?
No. Sister series such as WCA and WCI publish the same rows, so WCA and WCI each show 38. Collapsing identical case size, thickness, inductance pair and DCR values leaves 85 distinct falls out of 980 distinct steps.
Do you hold a Walsin datasheet for these inductors?
No. We hold 28 Walsin datasheets, 451 pages, covering 26 MLCC and 2 chip resistor series, and none covers an inductor. Every figure here is from the parametric export and should be confirmed against Walsin’s own pages and the datasheet for your exact part number.