Foldback (Snap-Back) TVS Cross-Reference: AMSEMI vs Littelfuse vs Vishay
One-line takeaway: foldback, snap-back and low-clamping all describe the same device behaviour — three vendors just use three different marketing names for it. AMSEMI calls it the -N series, Littelfuse calls it FlatSuppressX™ (TP5.0SMD-FL), and Vishay calls it XClampR®. If you need a DO-214AB (SMC) part across 24 V to 100 V that pin-to-pin replaces an existing 5.0SMDJ or SMDJ, the AMSEMI -N series currently has the widest grade coverage (23 grades at 5000 W, 13 grades at 3000 W, plus an 8000 W 8.0SMDJ tier). Littelfuse FL covers 4 grades at 5000 W; Vishay XClampR is a higher-power family that mostly lives in DO-218AB / DO-218AC packages.
Terminology: One Behaviour, Three Names
| Vendor | Family | What they call it | Physical behaviour |
|---|---|---|---|
| AMSEMI (Anhui Anmei) | 5.0SMDJ**CA-N · SMDJ**CA-N | foldback TVS (-N) | Snap-back I-V: Vc falls back below the initial breakdown knee |
| Littelfuse | TP5.0SMD-FL · TP1KSMB-FL | FlatSuppressX™ flat clamping | Foldback I-V characteristics, flat and stable clamp |
| Vishay General Semiconductor | XClampR® (XMC7K / XLD5A / XLD8A / XFD11K) | snapback TVS | Avalanche plus snapback, clamping ratio Vc/Vbr near 1.0 |
Why this matters for search and for sourcing: an engineer looking for a low clamping voltage TVS will often miss a vendor simply because that vendor markets the same physics under a different word. Foldback describes the shape of the I-V curve; low-clamping describes the result. They are the same product family.
I. The Three Low-Clamping Families at a Glance
| Vendor | Family | Package | Peak pulse power | Grade coverage |
|---|---|---|---|---|
| AMSEMI | 5.0SMDJ**CA-N | DO-214AB (SMC) | 5000 W (10/1000 μs) | 24–100 V, 23 bidirectional types |
| AMSEMI | SMDJ**CA-N | DO-214AB (SMC) | 3000 W (10/1000 μs) | 24–90 V, 13 bidirectional types |
| AMSEMI | 8.0SMDJ**CA-N | DO-214AB (SMC) | 8000 W (10/1000 us) | Vrwm 48-90 V, 11 bidirectional types, AEC-Q101 |
8000 W tier: AMSEMI's highest power class is the 8.0SMDJ series (8000 W at 10/1000 us, DO-214AB/SMC), giving extra energy margin on the same SMC land pattern. This tier is also an -N foldback series (8.0SMDJCA-N**, Vrwm 48-90 V, 11 bidirectional types), AEC-Q101 qualified with ESD +/-30 kV; automotive orders append -H to the base part number. Source: AMSEMI datasheet 8060057 (Rev. 2026-04-23). At the 54 V grade all three AMSEMI tiers clamp at 69.6 V and differ only in surge current: 34.4 A (3 kW), 57.5 A (5 kW) and 91.8 A (8 kW). | Littelfuse | TP5.0SMD-FL | DO-214AB (SMC) | 5000 W (10/1000 μs) | 54 / 58 / 60 / 64 V, 4 types | | Littelfuse | TP1KSMB-FL | DO-214AA (SMB) | 1000 W | Companion low-power version | | Vishay | XMC7K24CA | DO-214AB (SMC) | 7000 W equivalent | 24 V only | | Vishay | XLD5A24CA | DO-218AB | 7700 W equivalent | 24 V only | | Vishay | XLD8A24CA | DO-218AB | 11 000 W equivalent | 24 V only | | Vishay | XFD11KxxCA | DO-218AC | 11 000 W equivalent | 33–85 V, 15 types |
"Equivalent" is Vishay's own wording: XClampR parts are rated by the peak pulse power a conventional TVS would need to deliver the same current, not by a literal Pppm number in the datasheet. AMSEMI and Littelfuse rate their SMC parts at a true 5000 W / 3000 W / 1000 W Pppm. Do not compare the two numbering systems directly.
II. Where They Actually Overlap: 24 V Grade
The 24 V grade is the only place where the AMSEMI SMC foldback part and a Vishay SMC XClampR part sit side by side in the same package.
| Parameter | AMSEMI 5.0SMDJ24CA-N | Vishay XMC7K24CA |
|---|---|---|
| VWM (stand-off) | 24 V | 24 V |
| VBR range | 26.7–29.5 V | 26.7–29.5 V |
| Max clamping voltage Vc | 31.1 V @ 129.0 A | 24.0 V @ 180 A |
| Peak pulse current Ipp | 129.0 A (10/1000 μs) | 180 A (10/1000 μs) |
| Package | DO-214AB (SMC) | DO-214AB (SMC) |
Read this honestly: at 24 V, Vishay XMC7K24CA clamps lower (24.0 V) and carries more current (180 A) — it is a more aggressive snapback design and is rated to a higher equivalent power. Its Vc sits below its own VBR minimum, which is the signature of a deep snapback. The AMSEMI part clamps at 31.1 V at 129 A. If your 24 V rail needs the absolute lowest residual voltage in an SMC footprint and you can accept the Vishay supply chain, XMC7K24CA is the stronger part on paper. Where AMSEMI wins is coverage: Vishay's SMC XClampR stops at 24 V, while the -N series runs from 24 V all the way to 100 V.
III. Where They Actually Overlap: 54 / 58 / 60 / 64 V Grades
These four grades are where AMSEMI and Littelfuse meet — the same package, the same 5000 W class, both bidirectional, both AEC-Q101.
| VWM grade | Littelfuse part (Vc) | AMSEMI part (Vc) | Vc difference |
|---|---|---|---|
| 54 V | TP5.0SMD54CA-FL (68.5 V) | 5.0SMDJ54CA-N (69.6 V) | +1.1 V (+1.6%) |
| 58 V | TP5.0SMD58CA-FL (72.4 V) | 5.0SMDJ58CA-N (74.8 V) | +2.4 V (+3.3%) |
| 60 V | TP5.0SMD60CA-FL (77.7 V) | 5.0SMDJ60CA-N (77.4 V) | −0.3 V (−0.4%) |
| 64 V | TP5.0SMD64CA-FL (80.5 V) | 5.0SMDJ64CA-N (82.4 V) | +1.9 V (+2.4%) |
Both sides are at the same low-clamping level: the spread stays within ±3 V / ±3%. At the 60 V grade the AMSEMI part clamps marginally lower. Peak pulse currents track each other grade by grade (54 V: 57.5 A; 58 V: 53.5 A; 60 V: 51.6 A vs 51.7 A; 64 V: 48.4 A vs 48.6 A).
IV. Cross-Reference for the Industry-Standard 5.0SMDJ / SMDJ Naming
The 5.0SMDJ**CA (5000 W) and SMDJ**CA (3000 W) part numbers are an industry-standard naming convention in DO-214AB, used by multiple vendors (Littelfuse TP5.0SMDJ, Taiwan Semiconductor, AOS, Thinking, Kemet and others), not a proprietary code of any single maker. That is what makes cross-referencing possible: the same string maps to the same electrical grade across vendors.
AMSEMI parts follow the same convention, so a drop-in evaluation starts from the number you already have:
| VWM | Industry-standard part | AMSEMI foldback (-N) | Vc: standard to foldback |
|---|---|---|---|
| 54 V | 5.0SMDJ54CA | 5.0SMDJ54CA-N | 87.1 V → 69.6 V (−20.0%) |
| 58 V | 5.0SMDJ58CA | 5.0SMDJ58CA-N | 93.6 V → 74.8 V (−20.1%) |
| 60 V | 5.0SMDJ60CA | 5.0SMDJ60CA-N | 96.8 V → 77.4 V (−20.0%) |
| 64 V | 5.0SMDJ64CA | 5.0SMDJ64CA-N | 103.0 V → 82.4 V (−20.0%) |
| 75 V | 5.0SMDJ75CA | 5.0SMDJ75CA-N | 121.0 V → 96.8 V (−20.0%) |
Waveform caution: AMSEMI datasheets (8060014 standard, 8060055 -N) publish one waveform only, 10/1000 μs. Every Vc and Ipp on this page for AMSEMI is 10/1000 μs. Littelfuse publishes both 10/1000 μs and 8/20 μs for some of its own parts; Vishay publishes 8/20 μs surge capability for XFD11KxxCA (up to 2140 A). Never compare a 10/1000 μs clamping voltage against an 8/20 μs number — check the waveform on every column before you put two numbers in the same row.
V. Selection Decision Flow
flowchart TD
A["Start: what is your rail voltage?"] --> B{"Is 24 V your only high-power rail?"}
B -->|"Yes, and SMC footprint"| C["Compare Vishay XMC7K24CA vs AMSEMI 5.0SMDJ24CA-N"]
B -->|"No"| D{"Which VWM grade do you need?"}
D -->|"54 / 58 / 60 / 64 V"| E["AMSEMI 5.0SMDJ-N vs Littelfuse TP5.0SMD-FL, within 3 percent"]
D -->|"33 to 85 V, very high power"| F["Vishay XFD11KxxCA, DO-218AC, 11 kW equivalent"]
D -->|"24 to 100 V, SMC, drop-in"| G["AMSEMI 5.0SMDJ-N, 5000 W, 23 grades"]
C --> H{"Is absolute lowest Vc the priority?"}
H -->|"Yes"| I["XMC7K24CA: 24.0 V at 180 A"]
H -->|"No, prefer grade coverage"| J["AMSEMI -N: 31.1 V at 129 A, up to 100 V"]
E --> K["Evaluate pin-to-pin, verify with surge test"]
F --> K
G --> K
I --> K
J --> KVI. Honest Differences to Verify Before You Commit
| Item | What to check |
|---|---|
| Package footprint | Vishay XClampR mostly uses DO-218AB / DO-218AC, not SMC. More PCB area, different thermal pad. |
| Grade coverage | Littelfuse FL currently 4 grades (54–64 V); AMSEMI -N 23 + 13 grades from 24 V to 100 V. |
| Junction temperature | Littelfuse FL and Vishay XClampR are rated to 175 °C; the AMSEMI -N series to 150 °C. Check against your real mounting temperature. |
| Waveform basis | AMSEMI publishes 10/1000 μs only. Vishay XFD11K publishes 8/20 μs up to 2140 A. State the waveform on every comparison. |
| Rating convention | Vishay "7000 W / 11 000 W" figures are equivalent conventional-TVS ratings, not literal Pppm. |
Vendor relationship note: per Intek, AMSEMI (Anhui Anmei Semiconductor Co., Ltd) supplies GPP and TVS chips to Vishay as its sole domestic (China) chip source. This is a distributor-side commercial statement — please confirm it with the manufacturers before relying on it for a sourcing decision.
Frequently Asked Questions (FAQ)
Q1: What is the difference between foldback TVS, snap-back TVS and low-clamping TVS?
They are three names for the same device behaviour. Foldback and snap-back describe the shape of the I-V curve, where the voltage falls back after the breakdown knee instead of rising with current. Low-clamping describes the result that engineers actually care about: a lower maximum clamping voltage Vc at the same surge current, which lets you specify lower-voltage MOSFETs, capacitors and regulator ICs downstream.
Q2: Is there a drop-in alternative to the Littelfuse FlatSuppressX TP5.0SMD-FL?
Yes. The AMSEMI 5.0SMDJ**CA-N series uses the same DO-214AB (SMC) package and the same 5000 W peak pulse power class, and it covers the same 54 / 58 / 60 / 64 V grades with clamping voltages within 3 percent of the Littelfuse FL parts. It also covers 24 V to 100 V in 23 grades, so grades the FL series does not offer (24 V, 36 V, 48 V, 70 V, 80 V, 100 V) are available.
Q3: How does the Vishay XClampR series compare with the AMSEMI -N series?
They target different corners. Vishay XClampR pushes for the deepest snapback and the highest power, with clamping ratios near 1.0 and equivalent power ratings of 7000 W to 11 000 W, but mostly in DO-218AB and DO-218AC packages rather than SMC, and its SMC member (XMC7K24CA) covers only the 24 V grade. The AMSEMI -N series stays inside DO-214AB at 5000 W and 3000 W and covers 24 V to 100 V, which suits BMS protection boards and telecom or energy-storage rails that already have an SMC land pattern.
Q4: Can I replace an industry-standard 5.0SMDJ or SMDJ part with the AMSEMI -N series without a board change?
Electrically yes, in most cases. The 5.0SMDJ and SMDJ strings are an industry-standard naming convention in DO-214AB, and the AMSEMI -N parts share the same package, peak pulse power, VRWM, VBR range and Ipp as the standard parts. The single difference is a lower maximum clamping voltage. Footprint and polarity are unchanged, so you can drop the -N part in and validate with a surge test on the actual board.
Q5: What waveform are the clamping voltages on this page based on?
Every AMSEMI figure on this page is 10/1000 μs, taken from datasheets 8060014 (standard) and 8060055 (-N). Littelfuse publishes 10/1000 μs figures for the TP5.0SMD-FL series and also lists 8/20 μs data for some parts. Vishay publishes 10/1000 μs peak pulse currents for XClampR and an 8/20 μs surge capability of up to 2140 A for XFD11KxxCA. Comparing numbers across vendors is only valid when both are quoted on the same waveform.
Sources
- Littelfuse TP5.0SMD-FL FlatSuppressX series product page
- Littelfuse 5.0SMDJ series datasheet (PDF)
- Vishay XClampR TVS Application Note (document 98386)
- Vishay 24 V XClampR TVS launch release (SMC and DO-218AB)
- AMSEMI datasheets: 5.0SMDJCA-N series (Doc. 8060055, Rev. 2026-04-23), SMDJCA-N series (Doc. 8060084), standard 5.0SMDJ series (Doc. 8060014)
- AMSEMI foldback TVS full series and cross-reference (Intek, English)
- Littelfuse TP5.0SMD-FL vs AMSEMI foldback TVS (Intek, English)
- How to select TVS for BMS protection boards (Intek, English)
- Surge protection for energy storage and BMS (Intek, English)
- 安美 -N 回扫 TVS 全系列与型号对照（中文）
Contact Us
For datasheets or samples of a specific grade, or a cross-reference review against the part you are using today, contact us. Send your rail voltage, surge test level and waveform, and we will match parts against actual clamping curves.
Shenzhen Intek Technology Co., Ltd — electronic components distributor and system solutions provider Tel / WeChat: 136-3264-8484 Address: 4F, Building 2, Jingwei Center, No. 309 Pingan Avenue, Pinghu Street, Longgang District, Shenzhen, China Web: www.intek.vip
Disclaimer: this page is technical information for engineers. All parameters are quoted from the manufacturers listed under Sources and are subject to change. Always verify against the current datasheet of the exact part you intend to buy, and validate with surge testing on your own board. Nothing here constitutes a procurement or design-warranty commitment.