You do not pick the Y class and the AC working voltage separately — the AC rating decides the class. Across the 367 safety certificated disc capacitors Walsin Technology (Walsin) publishes, every one of the 112 parts rated X1-400Vac is Y1 and none is Y2, and every one of the 137 parts rated X1-440Vac is Y2 and none is Y1. Only X1-500Vac offers both. That forecloses the usb pd charger components decision before you reach the capacitance table.
Venatech Limited, an authorised Walsin distributor in Hong Kong, holds Walsin’s disc capacitor parametric export of 929 rows and its MLCC export of 24,026 rows. This post is written from those. Every part number below is real. Counts are of part numbers, not pieces.
Can I choose the Y class and the AC working voltage independently?
No. We cross-tabulated the X1 rating against the Y class on all 367 safety parts, and three of the four AC ratings offer exactly one class.
| X1 rating | Y1 parts | Y2 parts | Match / mismatch vs a free class choice |
|---|---|---|---|
| X1-400Vac | 112 | 0 | Mismatch — Y1 only |
| X1-440Vac | 0 | 137 | Mismatch — Y2 only |
| X1-500Vac | 54 | 49 | Match — both classes available |
| X1-760Vac | 15 | 0 | Mismatch — Y1 only |
The reason is that the class and the voltage are both carried by the same two-letter series
code. AH is X1/Y1, AC is X1/Y2 and AS is X1/Y1 at the highest AC rating, and the voltage group
digit sits inside each of those series rather than across them. SL0AH150J060 is a 400 Vac Y1
part; SL0AC100J060 is a 440 Vac Y2 part; SL5AH100J060 and SL5AC100J060 are the Y1 and Y2
halves of the 500 Vac group. There is no 440 Vac Y1 part and no 400 Vac Y2 part to ask for.
For a USB-C PD charger this matters in one specific way. If your isolation scheme and your creepage drawing have settled on Y1 — reinforced, single fault tolerant — then on this catalogue your AC working voltage is 400 V or 500 V, not 440 V. If you have designed to 440 V because that is the usual 250 Vac mains derating, you are in the Y2 column whether you intended to be or not. The class decode itself is in X1/Y1 vs X1/Y2 safety capacitors.
What does each X1 rating actually give me?
Four ratings, four different shapes of offering. The 440 Vac Y2 group is the deepest and the 760 Vac Y1 group is a fifteen-part corner.
| X1 rating | Parts | Distinct capacitance values | Dielectrics | Capacitance span |
|---|---|---|---|---|
| X1-400Vac / Y1 | 112 | 33 | SL, Y5P, Y5U, Y5V | 15 pF – 4700 pF |
| X1-440Vac / Y2 | 137 | 36 | SL, Y5P, Y5U, Y5V | 10 pF – 10000 pF |
| X1-500Vac / Y1 | 54 | 33 | SL, Y5P, Y5U, Y5V | 10 pF – 3300 pF |
| X1-500Vac / Y2 | 49 | 36 | SL, Y5P, Y5U, Y5V | 10 pF – 4700 pF |
| X1-760Vac / Y1 | 15 | 13 | Y5P, Y5U only | 100 pF – 4700 pF |
Two things fall out of this. The 760 Vac group is the only AC group with no SL Class I dielectric at all — all 15 parts are Y5P or Y5U, so the lowest-drift option disappears exactly where the working voltage is highest. And at 500 Vac, moving from Y2 to Y1 costs you the top of the range: the Y2 half offers 820 pF, 6800 pF and 10000 pF, and the Y1 half offers none of the three. Every capacitance the 500 Vac Y1 parts cover is also covered by the Y2 parts. Upgrading the class at 500 Vac can only lose you values, never gain one.
YP0AS101K070 and YU0AS472M140 are two of the 15 760 Vac parts, at 100 pF ±10% and 4700 pF
±20%.
Which safety parts also carry a DC rating?
Only the 500 Vac group, on every row, plus 23 automotive parts at 440 Vac. The rest carry an AC rating and nothing else.
| X1 rating | Parts | Rows that also state 1500Vdc |
|---|---|---|
| X1-400Vac | 112 | 0 |
| X1-440Vac | 137 | 23 |
| X1-500Vac | 103 | 103 — all of them |
| X1-760Vac | 15 | 0 |
The 23 at 440 Vac are the voltage group 7 automotive variants. So of 367 safety parts, 126
state a DC withstand figure and 241 do not. A PD charger’s safety submission usually wants both
numbers. If you need the DC figure in the data rather than in a datasheet you have to go and
fetch, the 500 Vac group is the only one that gives it to you across the board, and that is a
reason to look at 500 Vac Y2 before 440 Vac Y2 even though the AC rating is higher than the
application needs.
Is there a surface-mount alternative to the leaded Y capacitor?
Yes, and the data file describes it misleadingly. Walsin’s
Safety Certificated Caps X1/Y2_(S2 series) is an MLCC, 173 part numbers, at 1808, 1812, 2211
and 2220. Its Rated Voltage column reads 5000 Vdc or 6000 Vdc — and that figure is not a
rated voltage at all. It is the impulse voltage. Walsin’s S2 approval sheet labels the field
“Impulse voltage”, states “502: 5000V Impulse Voltage”, and gives the real working voltage as
X1 310 Vac / Y2 250 Vac, with 1500 Vdc on all models.
| Part number | Form | Class | What the export’s rated-voltage column says | What the datasheet says | Match / mismatch |
|---|---|---|---|---|---|
SL0AC100J060 |
Leaded disc | X1/Y2 | X1-440Vac/Y2-250Vac | same | Match |
S242B102K502 |
SMD MLCC, 1808 | X1/Y2 | 5000Vdc | impulse 5 kV; working X1 310 Vac / Y2 250 Vac / 1500 Vdc | Mismatch — mislabelled column |
S242N100J502 |
SMD MLCC, 1808 | X1/Y2 | 5000Vdc | impulse 5 kV; working X1 310 Vac / Y2 250 Vac / 1500 Vdc | Mismatch — mislabelled column |
SL5AC100J060 |
Leaded disc | X1/Y2 | X1-500Vac/Y2-500Vac 1500Vdc | same | Match |
Across all 24,025 MLCC rows Walsin publishes, not one carries an AC voltage rating — including these, where the AC working voltage exists on the datasheet and simply never reaches the data file. So anyone building a BOM from the export alone will put 5000 Vdc on a drawing for a part whose working voltage is 310 Vac, and will conclude the part has no AC rating when it has one.
The surface-mount part is the one a compact 65 W adapter actually wants, because a leaded disc cap costs you height and a hand insertion step. It is approvable — and better documented than the leaded parts. The S2 approval sheet carries named TUV, UL and CQC certificate numbers, UL file E182369 among them, tested to EN 60384-14:2023, IEC 60384-14:2023 and UL 60384-14:2025 (Ed 3.0). A UL file number is checkable in UL’s own public database. All five certificate numbers and the full documentation audit are in AVL submission documentation.
What does the primary-side snubber and bulk side look like?
High-voltage MLCC, 4,095 part numbers from 200 Vdc to 4000 Vdc. For a PD charger the two steps that matter are 630 Vdc for a 400 V bus and 1000 Vdc for the snubber across the switch.
| Part number | Size | Dielectric | Capacitance | Tolerance | Rated voltage |
|---|---|---|---|---|---|
0805B101J631 |
0805 | X7R | 100 pF | ±5% | 630 Vdc |
0805B102K631 |
0805 | X7R | 1000 pF | ±10% | 630 Vdc |
1206B102J102 |
1206 | X7R | 1000 pF | ±5% | 1000 Vdc |
1206B472K102 |
1206 | X7R | 4700 pF | ±10% | 1000 Vdc |
1206B681J102 |
1206 | X7R | 680 pF | ±5% | 1000 Vdc |
177 parts sit at 630 Vdc and 170 at 1000 Vdc. X7R at these voltages loses a large fraction of its nameplate capacitance under bias, and the snubber is the one position where that error shows up as dissipation in the switch rather than as ripple — the derating curves are in MLCC DC bias and voltage derating. Specify the capacitance you need at the bus voltage, not at 1 V.
Which single safety part number has bad data?
One of the 367. We decoded the capacitance code out of every safety part number and compared it
with the Capacitance column: 366 agree and YU0AS103M190 does not. Its 103 code reads
10000 pF and the column says 1000 pF.
| Part number | Code in the part number | Capacitance column | Match / mismatch |
|---|---|---|---|
YU0AS102M080 |
102 → 1000 pF |
1000 pF | Match |
YU0AS103M190 |
103 → 10000 pF |
1000 pF | Mismatch — one of 367 |
YU0AS472M140 |
472 → 4700 pF |
4700 pF | Match |
It is a 760 Vac Y1 part, so it sits in the fifteen-part corner of the catalogue where there is
least room to pick something else. The body size digits also differ — 190 against 080 on the
1000 pF part — which is consistent with the larger value being the real one, but a body size is
not a specification.
What does Venatech add that the catalogue page does not?
Three things. First, the cross-tabulations above: a catalogue page lists what each part is, and it will not tell you that the class you want has already decided your AC rating, or that upgrading to Y1 at 500 Vac can only remove capacitance options. That only appears when the whole file is counted. Second, a dated snapshot of what is physically in Hong Kong, so the design decision and the availability decision happen in the same conversation. Third, lot and date-code traceability with a certificate of conformity on request, and original sealed packaging — which is what a charger programme’s safety file and incoming inspection both ask for.
We will not tell you a part is equivalent. We will show you where it differs, field by field, and the qualification decision stays with you. The safety capacitor range is on the Walsin disc capacitor range page.
The short version
The Y class is a consequence of the AC rating, not a free choice: Y1 only at 400 Vac and
760 Vac, Y2 only at 440 Vac, both at 500 Vac. Only the 500 Vac group publishes a DC withstand
figure on every row. The 760 Vac corner has no Class I dielectric. The surface-mount S2 safety
series shows 5000 or 6000 Vdc in the export’s rated-voltage column, but that is the impulse
voltage — its working voltage, X1 310 Vac / Y2 250 Vac / 1500 Vdc, is on the datasheet and reaches
no data file. One safety part number, YU0AS103M190, disagrees with its own
capacitance code.
Tell us the AC working voltage and the class your creepage drawing needs, and we will tell you whether both exist together in this catalogue before you lay out the board. Or send the charger BOM and we will mark the positions where the class and the voltage are not both available.
Faster than an email. The cross-reference tool takes a pasted list or a spreadsheet and returns Walsin candidates field by field, differences included. Ready stock shows what is physically in Hong Kong as a dated snapshot, so you can see straight away whether a line is a stock pull or a production slot. Qualification stays with you.
Frequently asked questions
Can I get a Walsin X1-440Vac Y1 safety capacitor?
No. All 137 of Walsin’s X1-440Vac safety disc capacitors are Y2 and none is Y1. Y1 is available at X1-400Vac (112 parts), X1-500Vac (54 parts) and X1-760Vac (15 parts). The class and the AC rating are both carried by the series code, so they cannot be selected independently.
Which Walsin safety capacitor AC rating offers both Y1 and Y2?
Only X1-500Vac, with 54 Y1 parts and 49 Y2 parts. X1-400Vac and X1-760Vac are Y1 only and X1-440Vac is Y2 only. At 500 Vac the Y2 half also offers 820 pF, 6800 pF and 10000 pF, which the Y1 half does not, so moving up to Y1 there can only remove capacitance options.
Do Walsin’s safety capacitors publish a DC withstand voltage?
126 of the 367 do. Every one of the 103 parts at X1-500Vac states 1500 Vdc, and 23 automotive parts at X1-440Vac state it too. The 112 parts at X1-400Vac and the 15 at X1-760Vac carry an AC rating only. If you need the DC figure in the data, the 500 Vac group is the one that has it throughout.
Is there a surface-mount X1/Y2 capacitor in Walsin’s range?
Yes, the S2 series, 173 MLCC part numbers at 1808, 1812, 2211 and 2220. Its export rated-voltage column reads 5000 or 6000 Vdc, but that is the impulse voltage — the datasheet gives the working voltage as X1 310 Vac / Y2 250 Vac with 1500 Vdc, and names TUV, UL and CQC certificates.
What dielectrics are available at X1-760Vac?
Y5P and Y5U only. The 15 parts at X1-760Vac are eight Y5P at ±10% and seven Y5U at ±20%, and the group has no SL Class I option. The other three AC ratings each offer SL, Y5P, Y5U and Y5V, so the lowest-drift dielectric disappears at the highest working voltage.
Which Walsin safety capacitor part number has a capacitance error?
YU0AS103M190. Its part-number code 103 reads 10000 pF and its Capacitance column reads 1000 pF. It is the only one of 367 safety parts where the two disagree, and it sits in the 15-part X1-760Vac group. Venatech has flagged it for written confirmation and recommends using neither figure until Walsin answers.
What high-voltage MLCC does a PD charger snubber use?
Walsin’s middle to high voltage series holds 4,095 part numbers from 200 Vdc to 4000 Vdc, with 177 at 630 Vdc and 170 at 1000 Vdc. 1206B102J102 is a 1000 pF ±5% 1000 Vdc X7R part at 1206. Specify the capacitance you need at the bus voltage, because X7R loses a large fraction of its nameplate under DC bias.
Three ways to get this answered today
1. Cross a part, free. Paste up to 500 part numbers, or drop an Excel or CSV file, into the free cross-reference tool. It is matched against Walsin’s published catalogue and returns candidates field by field, with every difference from your original stated rather than hidden. Filter by commercial or automotive grade, or for soft termination, high temperature, safety certified, high Q / low ESR or low profile. There is no login and no charge.
2. Send the whole BOM. Upload a BOM and request a quote and we will come back line by line — including the lines we cannot help with, which is usually the more useful half of the answer.
3. Check the shelf before you commit. Ready stock shows what was physically in Hong Kong as at 23 September 2026. It is a dated snapshot, never a live feed, and quantities are never permanent.
Why take our word for any of this? Don’t — check it.
Venatech Limited (威納電子有限公司) is an authorised Walsin Technology distributor in Hong Kong. Confirm that with Walsin rather than with us. On the safety capacitor series we hold UL file E182369, which is searchable in UL’s own public database, together with TUV certificates R50381780 and R50195920 and CQC CQC20001280137 and CQC20001280136, against EN 60384-14:2023, IEC 60384-14:2023 and UL 60384-14. We hold 28 Walsin datasheets, 451 pages, and we will send the one covering your part number. Shipments arrive in original sealed Walsin packaging with lot and date-code traceability, and a certificate of conformity is available per shipment on request.
We will also tell you what we do not hold, which no competitor publishes. REACH, SVHC, conflict minerals, PFAS, China RoHS, ISO 9001, IATF 16949, PPAP, IMDS and a Declaration of Conformity appear nowhere in those 451 pages. You would rather hear that from us now than from your own supplier-approval team later. AEC-Q200 is compliant in Walsin’s own words and never certified, we hold no manufacturer’s end-of-life or allocation list for any brand, and qualification in your own circuit stays with you. We will not tell you a part is equivalent. We will show you where it differs.
Venatech Limited · Unit 207, 2/F, Sun Ling Plaza, 30 On Kui Street, Fanling, N.T., Hong Kong · (852) 2628 4777 · Hong Kong, Shenzhen, Singapore and Jiangmen, with Chengdu in preparation.