HMC850LC3 - typical value of current on VR pin

Hi,

I moved your question in RF and Microwave community. salemdar would be able to help you.

Regards.

Hi,

Usually 2-3 mA is drawn from VR pin to adjust gain. The relation goes linear such that as the VR is increased more current is drawn. We dont have a characterisation for VR current vs voltage specifically for this part but an easy implementation would be choosing appropriate VR for your application  and inserting a series resistor to create a voltage drop referenced to the supply of the IC(for this case, insert a resistor between GND and VR)

Sinan 

According to the data sheet, positive or negative values of VR can be used. I feel like the resistor method cannot work for both. I am more concerned with generating positive VR values (higher Vptp out)

Please confirm that I am understanding correctly. Are you saying that a constant 2-3 mA is sourced from the VR pin (pos current coming out of pin) regardless of resistor placed? In other words, If I would like to see +.4 V on the VR pin, could I just place a properly sized Potentiometer to gnd on the VR pin and tune accordingly to get desired VR value?

Thanks,

Greg

S

Since the part is biased between GND and -3.3V, resistor method can only be used for VR<=0V values. If you want to apply a poisitive VR(0.4V i.e.) you need an external positive supply and a resistor to create drop to adjust 0.4V. Sourced current is constant with respect to VR voltage and current is always drawn from that pin.