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Those are good questions, and I don't have a single definitive answer for them. I'd start with putting an appropriate TVS (or maybe separate diodes to ground and 3.3 V) between C3 and S1. My reas...
Answer
#2: Post edited
by
Olin Lathrop
·
2022-01-28T18:00:57Z (almost 3 years ago)
- Those are good questions, and I don't have a single definitive answer for them. I'd start with putting an appropriate TVS (or maybe separate diodes to ground and 3.3 V) between C3 and S1. My reason for clipping there is because then this gets to work against the impedance of the inductor.
- Look carefully at the capacitance of the TVS or diodes, and reduce C2 accordingly. This is where separate diodes might be necessary if you can't find a suitable TVS that has less capacitance than C2 needs to be.
In the end, you need to test yourself. Fortunately, the high voltage discharge models are usually no more than a capacitor and resistor, so you can make your own with a high voltage supply. Several places I've worked over the years made jigs like that. At HP we called it the "fickle finger" test. Testing it yourself lets you do fast turn arounds, and gives you confidence you'll pass the real test at the certification company.
- Those are good questions, and I don't have a single definitive answer for them. I'd start with putting an appropriate TVS (or maybe separate diodes to ground and 3.3 V) between C3 and S1. My reason for clipping there is because then this gets to work against the impedance of the inductor.
- Look carefully at the capacitance of the TVS or diodes, and reduce C2 accordingly. This is where separate diodes might be necessary if you can't find a suitable TVS that has less capacitance than C2 needs to be.
- In the end, you need to test yourself. Fortunately, the high voltage discharge models are usually no more than a capacitor and resistor, so you can make your own with a high voltage supply. Several places I've worked over the years made jigs like that. At HP we called it the "fickle finger" test. Testing it yourself lets you do fast turn arounds, and gives you confidence you'll pass the real test at the certification company.
- <hr>
- <blockquote> It sounds as we will need to run this in a simulator or we'd be fumbling around in the dark</blockquote>
- Seems the opposite to me. You need some real experimentation. There are too many unknowns to allow sufficiently realistic simulation of high voltage transients. There are parasitic capacitances all over the place. Parasitic inductances also matter. Capacitors can be quite non-linear at high voltages, and leakage in various places may not be resistive anymore either. The biggest unknown is how exactly the RF switch input reacts to short term out-of-range spikes.
- All in all, this is a case where you need to use experience, intuition, and something called a "brain". Let the new kid play with the simulator while you actually fix the problem the old fashioned way by doing some real lab work.
#1: Initial revision
by
Olin Lathrop
·
2022-01-28T13:16:31Z (almost 3 years ago)
Those are good questions, and I don't have a single definitive answer for them. I'd start with putting an appropriate TVS (or maybe separate diodes to ground and 3.3 V) between C3 and S1. My reason for clipping there is because then this gets to work against the impedance of the inductor. Look carefully at the capacitance of the TVS or diodes, and reduce C2 accordingly. This is where separate diodes might be necessary if you can't find a suitable TVS that has less capacitance than C2 needs to be. In the end, you need to test yourself. Fortunately, the high voltage discharge models are usually no more than a capacitor and resistor, so you can make your own with a high voltage supply. Several places I've worked over the years made jigs like that. At HP we called it the "fickle finger" test. Testing it yourself lets you do fast turn arounds, and gives you confidence you'll pass the real test at the certification company.