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RF Switch in non supported state

RF Switch in non supported state

RF Switch in non supported state

(OP)
Hi, I want to use an RF Switch that has two control signals A,B and supports only two states (RFC to RF1 and RFC to RF2)according to the input voltages at A,B. What would happen if I put the same voltage at the two control lines(0 Volts at A and 0 Volts at B). I want the switch to be off! I haven't found a switch that has the unused states defined. But I need to have it off when I want to...

the switch is :
http://www.hittite.com/products/view.html/view/HMC197

Thanks alot!  

RE: RF Switch in non supported state

Why?  I can think of no valid reason to try and use a chip's undefined states, and trying to use such logic is a guaranteed recipe for disaster down the line.

Modify your circuit to always ensure the chip's lines are in a valid state.  If you need the switch off and the chip doesn't allow that state, you need to disable the inputs to the chip, plain and simple.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: RF Switch in non supported state

You might find this app note useful...

"Simple Bias Circuit Creates "ALL-OFF" State for HMC436MS8G" (54KB) at the bottom of the page.

http://www.hittite.com/support/application-notes.html

Might be applicable to your part.  Contact Hittite to be sure.

RE: RF Switch in non supported state

(OP)
Thanks a lot for the help,the switch I want is just like the
HMC349 except that I want a lower power one (in order to keep the consumption of the circuit low).  

RE: RF Switch in non supported state

Um, careful with substituting these switches.  The HMC197 is a reflective switch (presents a short to the non-selected port).  The HMC349 and PE4257 are both non-reflective switches (presents a matched (50 ohm) impedance to the non-selected port).

Not the same.  Which favor do you need?

 

RE: RF Switch in non supported state

(OP)
Thanks a lot again. I will substitute the switch I used with the HMC349(I guess a non reflective switch is better)...:)

RE: RF Switch in non supported state

(OP)
Are there any bidirectional rf amps? I have only one Tx/Rx path.

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