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ADF4355 DC Bias

Question asked by on Nov 10, 2015
Latest reply on Nov 11, 2015 by

Dear Analog Devices,


I have a few questions regarding the Analog/Digital 3.3V power rail for the ADF4355:


1) Looking at the table below, the 3.3V supply current is up to 170.8mA (when Divider = 64). I assume this is when RFoutA is active and RFoutB inactive, am I correct?


2) Is the aforementioned current the total current drawn from the 3.3V supply? Does the VRF (pin 10) draw any extra current? Does this include both IRF and IRFout? Are IRF and IRFout the same thing or is there a difference? In other words, are the current values listed in the right-hand column the maximum ones, or do either of Vout (3.3V at RF output) and VRF have any extra current contributions?


3) Since we are about to design with this device for a wide-band application, up to 6GHz, what does your experience dictate with regards to the power rails of the 3.3V Analog (AVdd) and Digital (Dvdd)? Do you think they need to be supplied via the output of the same LDO regulator or is it preferable to be supplied separately, from two different LDOs?


Your response would be greatly appreciated.