• Resolved

TRF3722: several questions on TRF3722

Part Number: TRF3722

Hi dear supporting team,

customer has below questions on TRF3722, need double check with you:

1.  in d/s, there is only max input ref of 350MHz, what's the minimum frequency input? could it accept 10MHz?

2.  if do not use LO_OUT, could it be floating?

3. for the ferrite bead of the power supplies,  should customer add them all? and how to select the value of ferrite bead?

tks a lot!

  • Vera,

    I will take a stab at answering these questions. Russell can chime in later if the answers are not complete.

    1. The lower input may also be limited by the AC coupling path (i.e. ac coupling capacitor) in the PCB. You have to also keep in mind that the lower the PFD, the lower the phase noise performance. Typically, the customer may want to increase the reference frequency and PFD accordingly to optimize phase noise performance.

    2. LO output is open collector. It is best to tie the unused output to 3.3V to avoid transistor drifting.

    3. there are many different sections of the chip, i.e. PFD, PLL, VCO tank, and digital side and to prevent power supply coupling, it is best to isolate the rails with ferrite beads.