Add your comments about the Circuit Note found at http://www.analog.com/en/circuits-from-the-lab/CN0174/vc.html.
mostly, consumer applications is applied to reduce price and keep performannace.
so I think that application should be applied passive loop filter in consumer market.
at automotive rader application, when active loop filter does not use, what happened?
If have some check point in automotive radar,please advise me?
thank you very much.
An active filter is only needed where the tuning range of the VCO is wider than the tuning voltage of the PLL's charge pump.
For automotive radar it really depends on the VCO being used. In some cases you can get away with tuning over a smaller
range say 1V to 5V to get your required frequency range, in which case the ADF4158 charge pump voltage is sufficient.
Also we are sampling a new device called the ADF4150HV which has a 20V+ tuning range. This would be used with a passive
filter to directly tune wideband VCOs.
I have tried this configuration with an ADF4108, however when the power supply is disconnected the information stored in the chip is lost and has to be reprogrammed. It says applications are for automotive and mobile systems which require non-volatile systems, especially in the military. Is there a solution to this problem or have I misunderstood the capability of these synth chips?