Control of external GaAs switches with ADAR1000

Question

I'm considering to the use an external GaAs switch along with the ADAR1000 in order to have an external LNA and a PA. GaAs switches require two complementary voltages to control the signal path (PA to ANT or ANT to LNA). In my case, to set the TX path I need to set VA=0.5V and VB = -5V and to switch the RX path I need to reverse the voltages, i.e. VA=-5V and VB = 0.5V. 
 
 After carefully reading the ADAR1000 datasheet (page 38), I found that it provides two pins for driving an external GaAs switch: 
 TR_SW_POS = {0, 3.3} V 
 TR_SW_NEG = {-5, 0} V 
 
 TR_SW_POS and TR_SW_NEG are mutually exclusive (datasheet, page 42) so I can't have two wires, one with Vhigh and the other with Vlow, at the same time: 
 
 Can the ADAR1000 provide two simultaneous voltages as I mentioned above to drive a GaAs switch? If so, do you have an application example for the ADAR1000 with an external GaAs switch?

jdobler · Accepted Answer

Logic wise I think this would work and you control both pins in Register 0x31, so they should change at the same time. 
 Do know both pins have 1mA of available push/pull current.)

jdobler · Answer

The ADAR100 TR_SW pins were not intended to drive GaAs switches, but rather drive silicon switches like the ADRF5024 or ADRF5026. These switches only need a single control voltage. The examples given would use the TR_SW_POS pin. 
 Would a slicon switch have high enough linearity and compression to meet you application needs? The switches listed as examples are operational through 44 GHz.

Electronic Design Services - PartnerZone

Products In This Thread

Control of external GaAs switches with ADAR1000

Top Replies