USBLC6-2SC6 PCB Design Guide: Footprint, Pinout, and Alternatives
Low-capacitance ESD protection for two USB 2.0 data lines and VBUS
USBLC6-2SC6 is ST's SOT23-6L protection array for two high-speed data lines and VBUS. Its rail-to-rail diode network is built for USB 2.0 at up to 480 Mb/s, with 3.5 pF maximum capacitance from each I/O to ground and tight channel matching. ST rates the device itself to IEC 61000-4-2 level 4: 15 kV air discharge and 8 kV contact discharge.
The part is simple, but layout decides whether it works. Put it next to the connector, keep the ground return short, and route the data pair through the protected nodes without stubs. The ESD rating belongs to the component. A finished board still needs system-level testing because connector geometry, enclosure seams, and current-return paths can overwhelm a good protection diode placed badly.
What breaks boards
Put the protector at the connector
Route connector-side D+ and D- into USBLC6-2SC6 before the protected traces reach the USB transceiver. Long stubs or placing the array beside the transceiver leaves more copper exposed to the ESD current path.
Give pin 2 a short, low-inductance ground path
The steering diodes can only clamp as well as the return path allows. Connect GND directly to the ground plane with a nearby via instead of sending surge current through a long neck or shared signal return.
Connect VBUS even when the protected IC is self-powered
The rail-to-rail topology steers positive data-line surges toward the device's VBUS node. Leaving pin 5 floating defeats the intended clamp path; follow the datasheet schematic and manage the surge current on VBUS.
Do not swap the SOT23-6L and SOT-666 footprints
USBLC6-2SC6 is the SOT23-6L orderable. USBLC6-2P6 uses SOT-666 and a different land pattern, even though both devices implement the same two-line protection function.
Treat the ESD number as a device rating, not a finished-product certificate
The 15 kV air and 8 kV contact figures are device-level IEC 61000-4-2 ratings. Enclosure seams, connector geometry, grounding, and PCB current paths still decide whether the complete product passes system testing.
Key specifications
| Parameter | Value | Source |
|---|---|---|
| Orderable identity | USBLC6-2SC6; SOT23-6L; active and in volume production | ST USBLC6-2 product page, Product selector; checked 2026-07-10 |
| Protected lines | Two high-speed data lines plus VBUS | DS4260 Rev. 7, Features and Figure 1, page 1 |
| Data rate | USB 2.0 high speed up to 480 Mb/s | DS4260 Rev. 7, Applications and USB 2.0 compliance section, pages 1 and 7 |
| I/O capacitance | 2.5 pF typical, 3.5 pF maximum from I/O to GND | DS4260 Rev. 7, Electrical characteristics, Table 4, page 4 |
| Capacitance matching | 0.015 pF typical I/O-to-GND capacitance difference | DS4260 Rev. 7, Electrical characteristics, Table 4, page 4 |
| Leakage current | 10 nA typical, 150 nA maximum at VRM = 5.25 V | DS4260 Rev. 7, Electrical characteristics, Table 4, page 4 |
| Breakdown voltage | 6 V minimum from VBUS to GND at IR = 1 mA | DS4260 Rev. 7, Electrical characteristics, Table 4, page 4 |
| Clamping voltage | 12 V maximum at 1 A and 17 V maximum at 5 A, 8/20 µs | DS4260 Rev. 7, Electrical characteristics, Table 4, page 4 |
| ESD rating | IEC 61000-4-2 level 4: 15 kV air discharge and 8 kV contact discharge | DS4260 Rev. 7, Features, page 1 |
| Junction temperature | -40°C to +150°C operating junction temperature | DS4260 Rev. 7, Absolute maximum ratings, Table 2, page 3 |
Verified against the manufacturer datasheet on 2026-07-10. Confirm the current revision before production use.
Alternatives
- USBLC6-2P6: The same two-line protection circuit in ST's smaller SOT-666 package. It needs a different footprint and assembly process.
- USBLC6-4SC6: A four-data-line member of ST's USBLC6 family for designs that need more channels. Verify capacitance, pinout, and package rather than treating it as a drop-in replacement.
- ECMF02-2AMX6: An ST two-line common-mode filter with ESD protection for interfaces that also need EMI filtering. Its function, package, and layout requirements differ from this rail-to-rail protector.
Common questions
- Where should USBLC6-2SC6 go on the PCB?
- Place it beside the external connector, before the protected traces travel across the board. Keep pin 2's ground path short and wide, avoid data-line stubs, and preserve the differential pair geometry through the device.
- Does USBLC6-2SC6 support USB 2.0 high speed?
- Yes. ST specifies USB 2.0 operation up to 480 Mb/s. Each I/O has 2.5 pF typical and 3.5 pF maximum capacitance to ground, with 0.015 pF typical channel-to-channel matching.
- What is the difference between USBLC6-2SC6 and USBLC6-2P6?
- The protection function is the same, but the packages and footprints differ. USBLC6-2SC6 uses SOT23-6L; USBLC6-2P6 uses the smaller SOT-666 package.
- Can VBUS be left unconnected?
- No. VBUS is part of the rail-to-rail clamp path and receives ESD protection itself. Connect pin 5 as shown in the data-sheet application schematic and provide a suitable path for surge current.
- Does the 15 kV ESD rating guarantee that my product will pass?
- No. ST gives a device-level rating of 15 kV air discharge and 8 kV contact discharge under IEC 61000-4-2. System results also depend on the connector, enclosure, grounding, layout, and return-current path.
Sources
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