Using a switch in an RLC circuit

Hi Everyone,

I'm building an RLC circuit for an RFID application. What I would like to do is have two inductor coils (only one will be operated at any given moment) in this circuit controlled by a switch.

This is the switch I'm considering using:

http://www.ti.com/lit/ds/symlink/tps22960.pdf

Do you guys think this will work? Or will it interfere with the RLC circuit?

Thanks in advance for any help.

Austin

I don't think it will work. The linked IC is intended to be used as a power switch and is not bidirectional. What is the RFID frequency?

Remember that an RFID coil even if just excited by 5V can have over 100V across it at resonance. This has an impact on what you can do in terms of switching.

With that low an "on" resistance, it almost could be used to switch tuned circuits.

Except of course for two sneaky little details, one of which is not mentioned in the datasheet because it does not matter for power switching, but does matter for high frequencies (Technically, "medium frequencies" in the case of RFID), and another that you may have missed - or may not.

The first is the capacitance of the switching FETs, which is likely quite considerable (and incidentally, non-linear).

The second is the arrangement whereby an output which is switched off, is actually switched to ground.

You cannot use a low voltage CMOS switch in an RFID circuit, the voltages are large as its a resonant circuit.

Consider a relay or perhaps SSR.

Mark,

That's the conclusion I was beginning to come to. I'll give it a try!

Thanks