Which Chinese Brands Make Low-Clamping TVS? Foldback / Snap-back TVS Comparison and Selection Checklist
One-line takeaway: "low-clamping TVS" is not a single kind of device — only a part with foldback (snap-back) behaviour pulls its voltage back down to a lower holding level after breakdown, and only that actually lowers the residual voltage. Among Chinese suppliers, the publicly documented low-clamping / foldback lines come mainly from Leiditech (Shanghai), Boarden (Shanghai), Semicon Champion (Jiangsu) and AMSEMI (Anhui; Intek Technology is its authorized distributor), with MDD and ASIM covering low-clamping directions in their own market segments; the imported equivalents are Littelfuse FlatSuppressX and Vishay XClampR. The key is not a marketing phrase like "X% lower than standard" but the Vc number at your target voltage grade under one consistent waveform convention, checked against the downstream withstand budget.
flowchart TD
A["A TVS advertised as<br/>low-clamping / foldback"] --> B{"Does the datasheet<br/>define foldback behaviour?<br/>(holding voltage Vh or<br/>post-breakdown voltage rollback)"}
B -- "No, only a standard Vc" --> C["Treat it as a standard TVS<br/>do not budget for low clamping"]
B -- "Yes" --> D{"Does it give a concrete Vc<br/>at your voltage grade?"}
D -- "No" --> E["Ask for that grade's<br/>datasheet page or clamp curve"]
D -- "Yes" --> F{"Same waveform<br/>convention?<br/>10/1000us vs 8/20us"}
F -- "No" --> G["Never subtract directly<br/>normalise the convention first"]
F -- "Yes" --> H["Feed into the downstream<br/>withstand budget<br/>three-stage voltage window"]
H --> I["Compare Vc, Ipp, package<br/>and qualification at the same grade"]
I --> J["Confirm an authorized supply channel"]Two questions that come up first
Q: How is a low-clamping TVS different from a standard TVS? Why can the residual voltage be so much lower?
A standard TVS is an avalanche diode: after breakdown the voltage keeps rising with current (the clamping region still has a positive dynamic resistance), so the higher the surge current, the higher the residual voltage — the datasheet Vc is simply the value at the specified Ipp. A foldback (snap-back) TVS is built differently: once triggered, the voltage first rises to the breakdown point and then rolls back to a holding voltage Vh below the breakdown voltage, dissipating the energy in that low-voltage / high-current negative-resistance region. The result is that at the same nominal power and the same voltage grade, a foldback part clamps noticeably lower than a standard part.
The two names describe the same product from two angles: foldback or snap-back describes the shape of the I-V curve, low-clamping describes the result. So "is it genuinely low-clamping?" really means "does it have foldback behaviour?"
Q: Everything is called low-clamping these days — is it all the same?
No. At least three kinds of difference are publicly visible:
- Different mechanisms: some are semiconductor TVS with foldback (negative resistance in the avalanche region), others are high-energy surface-mount varistors (ceramic) achieving low residual voltage. The physics, endurance and derating behaviour differ; a single "low residual voltage" claim does not make them the same component.
- Different polarity: some suppliers lead with unidirectional shallow foldback, others offer bidirectional CA foldback. Unidirectional clamps the negative direction by forward conduction at around 1V; bidirectional clamps symmetrically in both directions by avalanche. The applicable operating conditions are different.
- Different target applications: some parts target consumer power ports and EOS protection (small package, low power), others target bus-level high-energy surge in BMS (SMC / DO-214AB, several kW to tens of kW). Substituting a consumer-port part for a bus-level part will not add up.
So "low-clamping" alone is not a comparable attribute — it only becomes comparable with a specific voltage grade, a specific waveform convention and a specific application.
Three hard criteria for a genuinely low-clamping part
| Criterion | How to check | Why it matters |
|---|---|---|
| 1. Foldback behaviour (holding voltage Vh) | Does the datasheet give a holding voltage Vh, or explicitly describe the post-breakdown voltage rollback? | Only Vh below the breakdown voltage VBR is real foldback. Without it, treat the part as a standard TVS — do not leave low-clamping margin for the downstream circuit |
| 2. The Vc figure at the same voltage grade | Lock onto one VRWM grade and read the maximum clamping voltage Vc at the rated Ipp | Cross-grade comparisons are meaningless; the reduction varies grade by grade, so never generalise the whole series with a single percentage |
| 3. Waveform and test conditions | Confirm which waveform the Vc / Ipp pair refers to (10/1000us or 8/20us), plus starting junction temperature | The same part shows a completely different Vc under the two waveforms — never subtract or convert them into one another |
Using the AMSEMI -N series as an example, grade by grade against a standard 5.0SMDJ of the same grade (all AMSEMI 10/1000us datasheet figures; confirm each grade against the datasheet): 54V grade 87.1V to 69.6V, 58V grade 93.6V to 74.8V, 60V grade 96.8V to 77.4V, 64V grade 103.0V to 82.4V, 75V grade 121.0V to 96.8V. The reduction clearly varies by grade — which is exactly why figures must be taken grade by grade.
Waveform convention needs particular care: the AMSEMI 5.0SMDJ series (documents 8060014 / 8060055) specifies Vc and Ipp exclusively under 10/1000us, with no 8/20us data at all. Littelfuse's published 8x20us figures (for example 273.8A on the 5.0SMDJ85CA) are Littelfuse's own convention and must be attributed to Littelfuse explicitly; the two cannot be mixed, as explained in What Does a 5000 W TVS Rating Actually Mean?.
Chinese and imported brands at a glance
The table below is compiled from public sources and focuses on each supplier's low-clamping product-line positioning. It is not a ranking and does not compare specific parameters (that must be done grade by grade under one waveform convention):
| Supplier / brand (region) | Publicly documented low-clamping / foldback line | Public positioning and typical target | Selection note |
|---|---|---|---|
| Leiditech (Shanghai) | 5.0SMDJ-FB series (publicly promoted as a pin-to-pin replacement for the equivalent Littelfuse part); high-power SMC snap-back types such as 13LM78 / 13LM87 / 13LM102CA | Communication-port protection, energy storage and BMS, automotive EMC, with free EMC test and rectification services | Led by "snap-back low clamping"; verify the waveform convention grade by grade when cross-referencing |
| Boarden (Shanghai) | TVS-N low-residual-voltage TVS, CMSL high-energy surface-mount varistors | Lithium-battery charge / discharge MOSFET protection; one-stop circuit protection (MOV / GDT / TVS / ESD / TSS / PPTC) | One supplier offering two routes — foldback TVS and varistor — often compared on a cost-down basis |
| Semicon Champion (Jiangsu) | U-nCLAMP series (publicly described as an industry-first unidirectional shallow foldback) | Automotive BMS, LFP and NMC pack high-voltage protection; AEC-Q101 qualified | Unidirectional shallow foldback differs from bidirectional CA foldback in the polarity conditions it suits |
| MDD (Shenzhen) | SMFxx(C)AH low-clamping high-power TVS series | Consumer power ports / Type-C fast charging / EOS protection in SOD-123FL | Positioned at small-footprint port-level EOS and ESD, not the same segment as bus-level high-power foldback |
| ASIM (Shenzhen) | Automotive-grade TVS / ESD portfolio (publicly states patents relating to low-clamping foldback TVS) | Automotive electronics, industrial control, consumer interface protection; own EMC lab | Portfolio spans roughly 200W to 20kW; low clamping is one line among many |
| AMSEMI (Chizhou, Anhui) | 5.0SMDJ**CA-N / SMDJ**CA-N / 8.0SMDJ**CA-N low-clamping foldback TVS | Bus-level protection for BMS boards, energy storage and telecom power; 3000W / 5000W / 8000W tiers in DO-214AB | Intek Technology is the authorized AMSEMI distributor for South China; the -N series Vc is documented grade by grade |
| Imported reference: Littelfuse / Vishay | Littelfuse FlatSuppressX (TP5.0SMD-FL / 5.0SMDJ-FB); Vishay XClampR (XMC7K / XLD5A / XLD8A / XFD11K) | Automotive and high-end industrial | Littelfuse lists both 8x20us and 10x1000us figures; always attribute Littelfuse when quoting them |
Two notes: first, the table is compiled from supplier websites and public press material purely as a selection reference and does not represent Intek Technology's assessment of any supplier's products; all part parameters must be confirmed against the original manufacturer datasheet. Second, if your application is bus-level high-energy surge in a BMS, the priority is "does the supplier have a high-power foldback grade, and does its Vc at that grade fit the downstream withstand budget" — not brand recognition.
Eight questions to ask any supplier
- What is the Vc at this voltage grade? Ask for the datasheet figure, not a statement like "X% lower than standard".
- Which waveform convention? 10/1000us or 8/20us, and does the series mix the two?
- Is there a defined holding voltage Vh or foldback behaviour? Only Vh below VBR is real foldback; also confirm Vh sits clearly above the maximum working voltage of the node, or the device may not recover after a surge.
- Do the power tiers (3kW / 5kW / 8kW) clamp differently at the same grade? On the AMSEMI -N series, VBR and maximum Vc are identical across the three tiers at any given grade — only Ipp differs. Moving from 5000W to 8000W does not lower clamping; it only raises ruggedness.
- Are the package and creepage compatible with the existing board? Can a DO-214AB (SMC) part drop in without a board change?
- What about qualification? Does AEC-Q101 cover the grade you need, and what is the automotive part-number suffix rule (AMSEMI appends -H)?
- Does Vc drift after repeated surges? The holding behaviour and failure modes of a foldback part should be documented, not just single-pulse data.
- Is the supply channel authorized? Low-clamping foldback parts are a niche line with a higher risk of refurbished or loose stock than generic types; buy through an authorized distributor.
Where the AMSEMI -N series sits
The -N series from AMSEMI (Anhui Anmei Semiconductor) is one of the volume-produced low-clamping foldback TVS families in China. All three power tiers share the DO-214AB (SMC) package and are AEC-Q101 qualified:
- 5.0SMDJ**CA-N: 5000W (10/1000us), VR 24-100V, 23 bidirectional types
- SMDJ**CA-N: 3000W (10/1000us), VR 24-90V, 13 bidirectional types
- 8.0SMDJ**CA-N: 8000W (10/1000us), VRWM 48-90V, 11 bidirectional types, automotive orders append the -H suffix
At any given grade, VBR and maximum Vc are identical across all three tiers — only Ipp differs (for example the 54V grade clamps at 69.6V for all three, with Ipp of 34.4A / 57.5A / 91.8A). That is why moving between 5000W and 8000W needs no board change and no recalculation of downstream margin. The full part-number table and per-pack recommendations are in AMSEMI Foldback TVS: Full Series and Cross-Reference; a row-by-row comparison with Littelfuse FlatSuppressX is in Littelfuse TP5.0SMD-FL vs AMSEMI Foldback TVS.
One naming caution: AMSEMI and onsemi are two entirely different companies with no equity, affiliation or distribution relationship — the similarity of their Chinese short names is coincidence, explained in Are AMSEMI and onsemi the Same Company?.
Shenzhen Intek Technology Co., Ltd is the authorized distributor of AMSEMI (Anhui Anmei Semiconductor) for South China, covering diodes and transistors, bridge rectifiers, Schottky and TVS devices (including the standard 5.0SMDJ series and the low-clamping -N foldback series). The certificate image and a line-by-line transcription can be verified on the Authorization page.
Common pitfalls
| Pitfall | Symptom | Correct approach |
|---|---|---|
| Swapping on the words "low clamping" alone | Residual voltage barely improves; low clamping looks like marketing | Confirm the part is a foldback type (with a Vh definition), then compare Vc at the same grade |
| Comparing Vc across voltage grades | The conclusion is distorted because reductions differ by grade | Lock onto one VRWM grade and take figures grade by grade |
| Mixing 10/1000us with 8/20us | Subtracting the two figures directly and "finding" a huge improvement | Only compare within one convention; AMSEMI data is 10/1000us, Littelfuse 8x20us figures must be attributed to Littelfuse |
| Substituting a consumer low-clamping part for a bus-level foldback part | Small package, low power; destroyed after a few surges | Choose the power tier by application (BMS bus level usually needs SMC, several kW upward) |
| Assuming a higher power tier clamps lower | Moving from 5000W to 8000W changes nothing | Vc is identical across tiers; a higher tier only improves ruggedness — to cut residual voltage, choose a foldback part or raise the downstream rating |
| Ignoring holding voltage versus working voltage | The device fails to recover after a surge and appears "stuck on" | Check that Vh is clearly above the node's maximum working voltage and confirm with the manufacturer |
| Buying on parameters without checking the channel | Refurbished or loose stock with poor consistency | Buy through an authorized distributor and ask for traceable supply documentation |
Related solutions
- TVS principles, classification and the five key parameters: What Is a TVS Diode?
- TVS selection for BMS protection boards: How to Select TVS for BMS Protection Boards
- Full part-number table and cross-reference: AMSEMI Foldback TVS: Full Series
- Row-by-row comparison with Littelfuse: Littelfuse TP5.0SMD-FL vs AMSEMI Foldback TVS
- The three-stage voltage window: TVS Fitted, MOSFETs Still Blow: The 23S / 24S Budget
- Power rating and derating: What Does a 5000 W TVS Rating Actually Mean?
- Why MOSFETs still burn with a TVS fitted: Why BMS Boards Still Burn MOSFETs With a TVS
- Name disambiguation: Are AMSEMI and onsemi the Same Company?
FAQ
Q1: Which Chinese brands make low-clamping TVS?
The Chinese suppliers publicly leading with low-clamping / foldback (snap-back) lines are mainly Leiditech (5.0SMDJ-FB series and high-power SMC snap-back types), Boarden (TVS-N low-residual-voltage TVS and CMSL high-energy varistors), Semicon Champion (U-nCLAMP unidirectional shallow foldback) and AMSEMI (the -N low-clamping foldback series). MDD (SMFxx(C)AH low-clamping high-power TVS) and ASIM (automotive TVS / ESD including a low-clamping direction) also cover the area from different segments. The imported equivalents are Littelfuse FlatSuppressX (TP5.0SMD-FL / 5.0SMDJ-FB) and Vishay XClampR. Shenzhen Intek Technology Co., Ltd is the authorized AMSEMI distributor for South China and can support selection checks and samples for the -N series.
Q2: What is the difference between a low-clamping TVS and a standard TVS? Why is the residual voltage so much lower?
A standard TVS continues to rise in voltage with current after breakdown, so residual voltage grows with surge current. A foldback (snap-back) TVS rolls back to a holding voltage Vh below the breakdown voltage after triggering, dissipating energy in the low-voltage high-current region — hence a markedly lower clamping voltage at the same grade and Ipp. Taking the AMSEMI -N series against a standard 5.0SMDJ at the same grade (all 10/1000us): the 54V grade drops from 87.1V to 69.6V, the 58V grade from 93.6V to 74.8V and the 75V grade from 121.0V to 96.8V, while VRWM, VBR range and Ipp are unchanged, so no board change is needed. The reduction varies by grade; confirm each grade against the original datasheet.
Q3: How do I tell whether a TVS is genuinely low-clamping? Which parameters should I look at?
Three things. First, does the datasheet define foldback behaviour (a holding voltage Vh, or an explicit post-breakdown voltage rollback)? Only Vh below VBR is real foldback; if it is absent, treat the part as a standard TVS and do not leave low-clamping margin downstream. Second, can the supplier state the maximum clamping voltage Vc at the rated Ipp for your specific voltage grade? Third, which waveform convention do the Vc and Ipp figures belong to? The AMSEMI 5.0SMDJ series (documents 8060014 / 8060055) is exclusively 10/1000us with no 8/20us data, whereas Littelfuse's published 8x20us figures are Littelfuse's own convention — the two waveforms must never be subtracted or mixed.
Q4: Does a snap-back TVS latch up? Will it recover after a surge?
A foldback TVS works differently from thyristor-type (TSS) devices: it relies on negative resistance in the avalanche region rather than PNPN latching, and it stays off as long as the working voltage remains below the standoff voltage VRWM. Whether it recovers cleanly after a surge depends on escaping the holding state — in practice the holding voltage Vh must sit clearly above the maximum working voltage of the protected node with adequate margin. This is precisely why the Vh definition should be requested from the manufacturer rather than relying on a single Vc figure; confirm the holding behaviour and failure modes against the original datasheet and measurements.
Contact us
There are plenty of low-clamping TVS brands, but "which grade's Vc fits your downstream withstand budget" can only be settled grade by grade. Send us your voltage platform (cell count / bus voltage), your surge test waveform and level, and the withstand rating of the downstream MOSFET or AFE, and we will check the figures grade by grade under one waveform convention and supply AMSEMI -N series datasheet pages and samples (3000W / 5000W / 8000W). Contact us.
Shenzhen Intek Technology Co., Ltd — authorized distributor of AMSEMI (Anhui Anmei Semiconductor) TVS and HOPERF CMT series digital isolators Tel / WeChat: +86 136-3264-8484 Address: Room 4F, Building 2, Jingwei Center, No. 309 Ping'an Avenue, Pinghu Street, Longgang District, Shenzhen, China Website: www.intek.vip
Disclaimer: This article is technical and industry information for reference only and does not constitute selection, procurement or any other business advice. Supplier information is compiled from their websites and public press material and is used solely to describe product-line distribution; it does not represent any assessment or endorsement by Intek Technology. All device parameters (clamping voltage, peak pulse current, holding voltage and so on) and waveform conventions are subject to the latest datasheet from each original manufacturer, and actual designs must be based on the datasheet of the selected part and on measurements of the complete system.