RF Switch in non supported state

[pucca]

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!

 

[MacGyverS2000]

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

 

[pstuckey]

Take a look at the HMC349. I'm currently using it, and it has an enable pin to do what you're looking for (all off).

http://www.hittite.com/products/view.html/view/HMC349LP4C

Peter

 

[jimkirk]

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.

 

[pucca]

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).

 

[pstuckey]

Take a look at Peregrine, the PE4257 supports an all off state and has current consumption of 8 uA (vs 2 mA for HMC349).

http://www.peregrine-semi.com/content/products/wireless/wireless_pe4257.html

Peter

 

[jimkirk]

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?

 

[pucca]

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

 

[pucca]

Hi again! Using the swithces and a power divider I have a loss of 5 dB MAXimum. What type of amplifier should I use in order to balance this loss (which parameters should I consider most).....a general purpose like this one is OK?

http://www.freescale.com/files/rf_if/doc/data_sheet/MMG3001NT1.pdf?pspll=1

 

[pucca]

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