How does one make sure the PLL lock to the onboad 25 MHz clk on the AD9957.
The steps that am describing is for AD9910. Not sure whether it will be exactly the same for AD9957.
To ensure that the PLL is locked you have to do two steps:
1) First enable the crystal oscillator. For this you have to remove c51 and c52 from the board and solder two 0 ohm resistors at R4 and R11. Change jumper to XTAL mode.
2) Next you have to populate the on board multiplier PLL circuitry. I took a multiplication factor of 40(to generate 1GHz frequency signals) and designed the resistors and capacitors. An excel spreadsheet is given that will help you in the calculations.
Once you do these two steps, in the GUI control dialogue, enter 25Mhz as the input and enable the multiplier and select the appropriate multiplication factor(40 in my case) and load the value. The PLL lock indicator in the GUI would glow. Also once you load the values and if everything is right, the red and yellow box across the multiplier box must vanish indicating there are no new problems. Hope this helps!!
Thanks for the reply. The PLL locks when I'm using the usb, but it dies not when I configure the device externally.
Hello, First, the PLL lock detect operation is the same for both the AD9910 and AD9957 devices. Note sure I understand the issue completely. Can you elaborate more on this issue. Are you saying the PLL lock detect remains lock if you remove the REF CLK or disable the PLL. If so, that could happen. The lock detect is a bit that's continuously readback from a register via the GUI, however it's sampled by the system clock in PLL mode, So, if the PLL is disabled and the PLL lock detect is being readback it could latch the wrong way and indicate a lock state.
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