AnsweredAssumed Answered

AD9524 PLL2 is locked, but output is NG

Question asked by williamchen on Jun 3, 2011
Latest reply on Jul 12, 2011 by MFelmlee



Please see our scheme and give us a clue, thank you!


Here is our design:



1. We don't use REFA and REFB.

2. The VCXO always outputs 10MHz, and don't need OSC_CTRL.

3. The PLL1_OUT is OK(= 10M/2 = 5MHz).

4. PLL2 is locked

    The value of Readback Register (Address: 0x22C) is "1110010".

     It means:    (7) PLL2 reference CLK is OK

                       (6) PLL2 feedback CLK is OK

                       (5) VCXO status is OK

                       (4) REF_TEST is off/clocks are missing

                       (3) REFB is off/clocks are missing

                       (2) REFA is off/clocks are missing

                       (1) PLL2 is Locked

                       (0) PLL1 is unlocked

     The value of Readback Register (Address: 0x22D) is "00001000".

     It means "holdover" is active.


The output of CH2 is 100KHz.

  It seems the input of CH2 divider is 10MHz(10M/100=100K), not 1GHz(1G/100=10M).

  But the value of PLL1 output Control Register (Address: 0x1BB) is set to "0x00", choose the VCO as CH2 divider input.


  Please give us a hint or direction to debug.


  Thank you in advance!


  Best Wishes,