You can certainly use such devices. They are usually a poor choice for anything that has lower power usage requirements as they have high leakage current.
You also have to be careful of the clamping voltage, ESD of ~200V can damage a micro-controller, the device you linked is specced at 500V max. Make sure whatever your trying to protect is actually be protected to the extent it needs.
For digital lines also pay attention to the capacitance of these device/package, they can screw up your signal integrity.
What I usually do if the input is likely to get hit with ESD, like an input that is often connected in the field is use a 2 pronged approach.
First Use a ESD device, or diodes closer to the circuit to protect, which type I would use depends on the signal/circuit in question. This is to protect against lower spikes, say 8kV. More and more you see this type of protection inside devices, especially boundary devices like RS232 drives and line drivers.
Second, when you build the PCB use spark gaps, which is really nothing more than putting 2 pads on the surface of the PCB, 1 being the signal, the other being a good ground and spacing them very close to each other, like 6 thou apart. This will protect against higher voltage hits, like 25kV. Pretty simple concept, the high voltage jumps the gap and goes straight to ground. Just be careful how you place these, as close to the connector as possible with the best possible ground connection.
Also pay attention to the manufacturing process your using, you don't want solder to accidental bridge the gap.
Gaps can be tough to do on digital traces and avoid changing the impedance, usually requires tweaking the signal termination after the prototype run.
There is some argument over the proper shape of the pad, some use half moons, some use pointed triangles with the tips near each other and some use square pads. I've always used square pads, the more area that is close to the other pad the more repeated strikes the gap will survive. The trade off is that the square pads will take the most effort to ensure there is no solder bridging. Best answer is to get your CM to not apply solder to these pads at all, but that can require special effort on their part.
I'm not sure you are comparing apples with apples on this. The RS485 device is undoubtedly more powerful and clamps to a lower voltage than the USB device: -
- SM712 clamp voltage at 5A = +20V and -10V (reverse)
- PGB1 clamps at 150V from an 8kV contact discharge
I think I've said enough to establish you can't compare the devices electrically and therefore you can't make conclusions about the circuit symbols implying one is a significantly lower capacitance although undoubtedly the USB device is lower capacitance by a long way.
As far as I'm concerned both symbols are electrically the same and, as usual, the detail is in the small print on the data sheet.
Best Answer
USB pins need protection from ESD. Here is one solution using TVS devices.