Schematic is similiar to EVAL Kit. Integer mode. Fref=10MHz. Loading sequence: REG 06h: frac_rstb=0; buff_rstb=0; REG 03h: intg; REG 09h: setting cp_UPcurrent_sel, cp_DNcurrent_sel; REG 0Bh: pfd_phase_sel=1. Incoming data verified by reading procedure. We made sure that the changing of the charge pump current thru REG 09h impacts the CP Output. But we don't see the locked VCO output, LD=0, VCO output signal is on the upper rail and CP output is about 200 mV (600 mV when CP current=0).
Could you share an idea what happens ?
Thanks in advance, Dmitry Kuznetsov, RF department of Moscow Radio Research Institute/
Hello Mr. Kuznetsov,
Please note that this uses one of our older PLL's and as such the INT and FRAC registers are not double buffered so the change takes place immediately after the write. Please consult…
Please note that this uses one of our older PLL's and as such the INT and FRAC registers are not double buffered so the change takes place immediately after the write. Please consult the User Guide for additional information regarding use of an interim INT value and the proper sequence.
If you could please provide the register file arranged in the order that it is being written as well as the carrier frequency and loop filter schematic I may be able to help a bit more.
Have you reviewed the register settings shown in the User Guide, Operating Guide for the HMC807 and FAQ for the HMC700 (same functionality as PLL in HMC807)? If not I've attached them below.
best regards, Dmitry