Hi,
I've yet to use TVS in an application due to typically using two large back-to-back zeners. Investigating TVS diodes as a cleaner replacement it appears they are not merely drop-in. My questions are;
1. TVS appear to have a breakdown voltage much lower than the clamp point. For the 35V AC I want to clip at many TVS's begin at 18V. Granted this may be at minor current, however zener's don't have such a wide range (typically 5% variance).
2. It's not clear if TVS's shunt the entire voltage once they breakdown. I assume this isn't the case as it's not logical, so a 30V TVS supplied 40V will shunt 10V?
3. TVS's have a much higher power rating than zeners (which is why I ask 2.) but is this value for an ad-hoc spike rather than a SINE? In which case, could zener's actually be more tolerant than TVS's over time?
I should mention that I'm not expecting the input signal to be > 35V AC often or for long periods of time, say a minute tops, and even then it'll not be over by much, say 10V. Current is fixed at 500mA, so 5W dissipation.
Cheers,
Andrew
I've yet to use TVS in an application due to typically using two large back-to-back zeners. Investigating TVS diodes as a cleaner replacement it appears they are not merely drop-in. My questions are;
1. TVS appear to have a breakdown voltage much lower than the clamp point. For the 35V AC I want to clip at many TVS's begin at 18V. Granted this may be at minor current, however zener's don't have such a wide range (typically 5% variance).
2. It's not clear if TVS's shunt the entire voltage once they breakdown. I assume this isn't the case as it's not logical, so a 30V TVS supplied 40V will shunt 10V?
3. TVS's have a much higher power rating than zeners (which is why I ask 2.) but is this value for an ad-hoc spike rather than a SINE? In which case, could zener's actually be more tolerant than TVS's over time?
I should mention that I'm not expecting the input signal to be > 35V AC often or for long periods of time, say a minute tops, and even then it'll not be over by much, say 10V. Current is fixed at 500mA, so 5W dissipation.
Cheers,
Andrew