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AD9854: Relation between of LP filter and REF Multiplier

Question asked by d0ct0r on May 11, 2014
Latest reply on May 12, 2014 by d0ct0r



I would like to clarify the relation between of LP filetr on DAC output and Ref clock multiplier. I would like to keep the multipler value as low as possible for certain frequency range. My question is: is it necessary to use different LP filters on the DAC output for each multiplier value ?

Lets say I have 10 Mhz Ref clock. I could use multipler as low as 4 to cover any frequences from DC to 25Mhz. Then, if I need to generate 70Mhz sine wave, I'll need to change the multipler value to 20. Is it OK to use the same 70Mhz LP filer for both cases, or I need to implement TWO LP filters: one for 25Mhz and another one for 70Mhz. Please, advise ! Thanks !