Question
If we use the RF channel only, do we need to provide the power supply to IF
channel or can we leave the pins for IF channel float?
Answer
To avoid internal protection diodes being turned on – it is better to supply
power to the IF channel.
In this case just tie the IF power pins (Vdd2/Vp2) to the RF power pins.
When configuring the part the datasheet mentions (pasted below) you do not need
to write to the IF registers. this will ensure the IF channel stays in
powerdown. You can leave the IF input pins IFINa/IFINb floating.
All GND pins should be common.
“It is necessary to write only to Registers R3, R2, R1, and R0 when powering up
the RF synthesizer only. The IF side will
remain in power-down until Registers R6, R5, R4, and R3 are written to.”