ADF7020: AFC response time

Document created by analog-archivist Employee on Feb 23, 2016Last modified by analog-archivist Employee on Aug 10, 2016
Version 2Show Document
  • View in full screen mode

Could you please help to check  for AFC Response Time of ADF7020? It is marked
as 48 BITS on datasheet(page 5). Is there anything wrong with the unit? Is this
the time AFC spends to pull in the incorrect frequency to a correct value? (See
figure)

 

The AFC circuit can pull in frequency error of +/- 50kHz (in fact actual range
is more like +/-70kHz) but we are spec'ing 50kHz.
As the datasheet mentions you can get wider pull-in range for the wider IF BW
setting.
As regards the AFC response time, this typically takes 48 bit transistions for
IF to settle to 200kHz +/-1kHz (i.e. +/-1kHz error).
This is usually contained in the preamble. So if you are using AFC, you should
set the preamble to at least 48 bits.
It is possible to improve the AFC repsonse time using some of the register
settings if this is a problem.

Outcomes