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Problems when using HMC980LP4E eval board with HMC487LP5 eval board

Question asked by Frederikke.r on Jun 1, 2016
Latest reply on Jun 15, 2016 by Frederikke.r

I have a HMC487LP5E (PA) evaluation board. When I use an adjustable voltage supply and follow the application note on how to bias the PA it works perfectly and draws the expected 1300 mA with a gate voltage of appoximately -0.2 V and a 7 V drain voltage.


When I try to use the Active Bias Control (ABC) HMC980LP4E to supply the PA it does not work. When the ABC is not connected to the PA it gives out a drain voltage when enabled and a positive gate voltage (2.5 V). When it is unconnected and disabled the drain voltage is 0 V and the gate voltage is -2.5 V (as expected). When the PA is connected and the ABC is enabled VDRAIN is 0 V and VGATE is -0.7 V. I have tried adjusting RSENSE (R10 potentiometer). I have tried with S1=VDIG and S0=VDIG which would require a VDD of 7.9 V according to Table 1 in the datasheet of the ABC. I have also tried with S1=VDIG and S0=GND with a VDD of 8.1 V as given in Table 3 of the datasheet of the ABC for the HMC487 PA.


ALM is low in all cases and TRIGOUT is also low. Any suggestions on how I can find out what I am doing wrong?