bipolar tvs
bipolar tvs
(OP)
I'm looking for a bipolar TVS solution for ESD protection. While there are many bipolar TVS solutions available, are there any drawbacks to using two unipolar TVS in series with opposite polarity? I've seen three pin devices where you can hook the two devices in parallel (anodes tied together and cathodes tied together) or in series (only anodes tied together), so it seems two devices could work as well.
Other than more space requirements, are there any other gotchas? Both diodes are off until a pulse event happens, and then one has forward current and the other has reverse (avalanche) current while the pulse energy is dissipated. Turn on time for forward conduction is the only parameter that I can think of that may be an issue.
Thanks,
Z
Other than more space requirements, are there any other gotchas? Both diodes are off until a pulse event happens, and then one has forward current and the other has reverse (avalanche) current while the pulse energy is dissipated. Turn on time for forward conduction is the only parameter that I can think of that may be an issue.
Thanks,
Z





RE: bipolar tvs
Keith Cress
kcress - http://www.flaminsystems.com
RE: bipolar tvs
Z
RE: bipolar tvs
Keith Cress
kcress - http://www.flaminsystems.com
RE: bipolar tvs
http://www.semtech.com/circuit-protection/
RE: bipolar tvs
Have you checked out the 1.5KE series from littelfuse? They have a whole bunch of clamping voltage rated options, and are all rated for 6.5W steady state and 1500W peak power dissipation:
http://www.littelfuse.com/~/media/electronics/data...
Forgive me if this is old news for you since I think that vishay might make its own version of the 1.5ke series, which you might have seen already...
And just out of curiosity, may I ask you what your application is?
-Rob
RE: bipolar tvs
I only need about 0.3W steady state, but i have some very tight size restrictions.
Z
RE: bipolar tvs
1. Using two packcages in series, compared to 1 bi-directional package, may result in a bit more lead inductance so your peak voltage during ESD discharge may be a bit higher. Ultimitely, your test will confirm the pass/fail result.
2. Generally, ESD is a CE and/or EMC requirement only, not for IS. Therefore, as long as the failure of the ESD diode (open or short) does not result in an unsafe condition, the part does NOT need to be rated according to the IS standard (I assume 60079-11 or similar). Remember, those component sizing rules and tests only apply for components which intrinsic safety relies. Of course, if you are using the same diodes to maintain an intrinsically save voltage, then you need to go through the analysis.
RE: bipolar tvs
2) The feedback I'm getting from my Intrinsic Safety expert is that the TVS needs to be rated to withstand the steady state fault power without letting the smoke out. I believe this is because uncountable faults could apply the fault power directly to the TVS leads. Encapsulating the TVS may be a solution but I'm hoping to avoid encapsulation.