Passive Components for an EV On-Board Charger: AEC-Q200 MLCC, Resistors and MOVs

148 of Walsin Technology’s 2,294 AEC-Q200-compliant MLCC are rated 500 Vdc or higher — the band an OBC’s PFC and DC-link stage actually needs. The other 2,146 AEC-Q200 parts top out at 250 Vdc and belong on the low-voltage control board, not the power stage. The 788-part MG series is automotive-grade but carries no AEC-Q200 compliance at any voltage, so it never enters this count regardless of its rating.

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Venatech Limited, an authorised Walsin distributor in Hong Kong, holds Walsin Technology (Walsin) full MLCC, chip resistor and MOV parametric exports plus 26 MLCC datasheets. This post is written from those files for the three passive families an EV on-board charger (OBC) design review actually checks: AEC-Q200 MLCC on the high-voltage side, high-voltage chip resistors in the sensing network, and MOVs on the AC input. Every part number below is real and every count is of part numbers, not pieces.

Which Walsin MLCC are both AEC-Q200 compliant and rated for the OBC DC link?

148 parts, out of 24,025 MLCC in the catalogue. Walsin publishes AEC-Q200 compliance on two MLCC series — Automotive MT (2,176 parts) and Automotive Soft Termination ST (118 parts), 2,294 combined. Of those, 131 MT parts and 17 ST parts are rated 500 Vdc or above, the band that covers an OBC PFC stage and 400 V-class DC link with margin. That is 6.5% of the AEC-Q200 MLCC pool.

Series	AEC-Q200 compliant	Total parts	≥500 Vdc parts
MT (Automotive, AEC-Q200)	Yes	2,176	131
ST (Soft Termination, AEC-Q200)	Yes	118	17
Combined	—	2,294	148

The 2,294 figure counts rows in Walsin’s export. Three of those rows are duplicates, so the AEC-Q200 line is 2,291 distinct part numbers. All 148 parts at 500 Vdc or above are distinct.

Sample part numbers at 630 Vdc and above, 1206 and 1210 case sizes:

Part number	Series	Case	Dielectric	Capacitance	Voltage	Match / mismatch
MT31B101K631	MT	1206	X7R	100 pF	630 Vdc	Match — AEC-Q200, DC-link voltage
MT31B472K631	MT	1206	X7R	4700 pF	630 Vdc	Match — AEC-Q200, DC-link voltage
MT32B103K102	MT	1210	X7R	10 nF	1000 Vdc	Match — AEC-Q200, DC-link voltage
ST31B472K102	ST	1206	X7R	4700 pF	1000 Vdc	Match — AEC-Q200, DC-link voltage, soft termination
MT31N152F631	MT	1206	NPO	1500 pF	630 Vdc	Mismatch — same case and voltage, thicker body (1.60 mm vs 1.25 mm on the X7R part above)

Source for the AEC-Q200 compliance statement and the voltage range: WTC_MLCC_Automotive_MT.pdf and WTC_MLCC_Soft_term_Auto_AECQ200_ST.pdf.

Why doesn’t the MG series not count, even at the same voltage?

Because Walsin’s own series name says so: “Automotive Caps Without AEC-Q200 Certification (MG series).” It is a real, automotive-grade line — 788 parts — and nine of them are rated 500 Vdc or above. None of the nine can substitute for an MT or ST part in a design that requires AEC-Q200, no matter how closely the electricals line up.

The closest pair in the catalogue makes the point directly. MT31B472K631 and MG31B472K631 are both 1206, X7R, 4700 pF, 630 Vdc, with identical published length, width and thickness:

Part number	Series	Case	Capacitance	Voltage	L × W × T (mm)	AEC-Q200	Match / mismatch
MT31B472K631	MT (AEC-Q200)	1206	4700 pF	630 Vdc	3.20×1.60×1.25	Compliant	—
MG31B472K631	MG (no AEC-Q200)	1206	4700 pF	630 Vdc	3.20×1.60×1.25	Not compliant	Mismatch — qualification only

Every dimension and electrical rating published in the parametric export matches. The only difference a BOM reviewer will find is which datasheet the part sits under, and that is the one that matters for an automotive power stage.

What covers the AC input surge on an OBC?

Walsin’s varistor line gives sized options at both common AC input bands. At 275 Vac — a 230 Vac single-phase line with standard margin — and at 420 Vac — a 400 Vac three-phase line — the Standard (D), High Energy (E) and Industrial series scale peak current with body size:

Part number	Series	Size	Max working voltage	Varistor voltage	Peak current	Match / mismatch
SR431K05D	Standard (D)	5 mm	275 Vac	430 Vdc	400 A	Smallest footprint, lowest surge capacity
SR431K10D	Standard (D)	10 mm	275 Vac	430 Vdc	2500 A	Match for a mid-power single-phase OBC input
SR431K32D	Industrial	32 mm	275 Vac	430 Vdc	30000 A	Mismatch on footprint — through-hole industrial body
SR681K10D	Standard (D)	10 mm	420 Vac	680 Vdc	2500 A	Match for a three-phase 400 Vac OBC input
SR681K20D	Standard (D)	20 mm	420 Vac	680 Vdc	6500 A	Higher surge margin, larger footprint

Varistor voltage is the DC reference point on the clamping curve, not the AC working voltage — size the part on the Max Working Volt. column for your actual line voltage, and leave margin above the steady-state RMS value.

Which chip resistors handle the high-voltage sensing network?

Walsin’s Thick Film High Voltage Chip Resistor (Automotive) series — 6,803 parts — covers the bleed and divider resistors a high-voltage sensing network needs, across 0603 to 2512 case sizes, with a UL Safety Certification variant adding another 1,502 automotive parts:

Part number	Series	Case	Resistance	Rated power	TCR	Match / mismatch
WK08V47R0GTLJ	High Voltage (Automotive)	0805	47.0 Ω	1/8 W	≦±200	Match — small-footprint sensing
WK12V47R0GTLJ	High Voltage (Automotive)	1206	47.0 Ω	1/4 W	≦±200	Match — same resistance, higher power
WK25V47R0GTLJ	High Voltage (Automotive)	2512	47.0 Ω	1 W	-200～+500	Mismatch on TCR — wider band at this case size
WK25V47R0DTL	High Voltage (commercial)	2512	47.0 Ω	1 W	—	Mismatch — not the automotive series

The schema has no rated-voltage column at all; “High Voltage” is a series-name label, exactly like the “(Automotive)” marker on the same files. There is no numeric field to filter on for either property — both have to be read from the Series text.

What’s the smallest AEC-Q200 case size that clears 1000 Vdc?

1210, on the MT series. Within the 148-part AEC-Q200-and-high-voltage pool, 0805 tops out at 630 Vdc (11 parts), 1206 reaches 1000 Vdc on MT (5 parts) and up to 1000 Vdc on ST, and 1210 is the smallest case carrying a 1250 Vdc part — MT32N103J12E, NPO, 10 nF. Above 1000 Vdc the ST series adds 1812 and 2220 case sizes rated to 3000 Vdc, outside the 148-part DC-link count above because that voltage band belongs to isolation barriers, not the DC link itself.

For the same case-size breakdown across Walsin’s full high-voltage MLCC catalogue, not just the AEC-Q200 slice, see Middle and High Voltage MLCC, 200V to 4kV.

Does Walsin certify these parts to AEC-Q200?

No. Walsin’s MT and ST datasheets state AEC-Q200 compliance, not certification — the standard itself does not issue third-party certificates. Compliant means Walsin ran the qualification testing in-house against the standard’s test plan; it does not mean every lot or every part number automatically carries a current report. Ask Walsin for the qualification report covering the exact part number, case size and voltage you intend to buy, and check its revision date. Venatech makes no AEC-Q200 claim of its own — the qualification belongs to Walsin, and the report is the only document worth relying on.

For what the standard actually covers, see AEC-Q200 MLCC: MT vs MG series. The full automotive MLCC range is on the Walsin MLCC range page, and varistors are on the MOV range page.

The short version

An AEC-Q200 claim and a high-voltage rating are two separate filters, and only 148 of Walsin’s 24,025 MLCC clear both at 500 Vdc or above. The MG series is automotive-grade but is explicitly excluded from AEC-Q200 by Walsin’s own series name, even when a part number is otherwise identical to an MT part. High-voltage automotive chip resistors exist in volume but carry no datasheet we hold, so confirm their qualification status before you design one in. MOVs size against Max Working Volt., not varistor voltage, and Venatech holds no MOV datasheet at all.

Send us your OBC BOM and we will tell you, line by line, which Walsin parts clear AEC-Q200, which clear your voltage class, and which clear both. Or give us one incumbent part number and ask us to check it against the 148-part pool above.

Check it against the catalogue yourself. Cross-reference accepts one part number or a whole BOM column and prints the mismatches as plainly as the matches — qualification stays with you, which is the honest division of labour. Ready stock covers the ceramic capacitor lines held in Hong Kong.

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Frequently asked questions

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