Hi,
I am planning to use a XO (50MHz) connected to LMK03806. then LMK03806 will distribute the clock to FPGA, ADC, DAC etc. So I need a startup clock to program LMK03806 and used the programmed clock as FPGA system clock.
I have some questions below.
1. In the datasheet "8.3.6 Default Start-Up Clocks", "When an XO or other external reference is used as a reference with OSCin, OSCout0 will buffer the OSCin frequency in addition to CLKout8 operating at a nominal VCO frequency/25." "The nominal VCO frequency of CLKout8 on power up will typically be 98 MHz."
Q1: Does it means the power up clock will be fixed at 98MHz/25 =3.92 MHz, no matter what the XO frequency is?
2. "Note during programming CLKout8 may momentarily stop or glitch during the VCO calibration routine."
Q2: If I use the 3.92MHz power up clock from CLKout8 to program LMK03806, is this clock available when I programming it? I guess the code is first written to some shadow registers in LMK03806, when the power up clock should be available, and then a strobe signal to update the register with shadow register code, when the power up clock will be unavailble. But I need a confirmation.
3. I was thinking the use the buffer clock at "OSCout0/1" to clock FPGA directly. But in "8.3.2 Crystal Support With Buffered Outputs", "Crystal buffered outputs cannot be synchronized to the VCO clock distribution outputs".
Q3: Does it means this FPGA clock will not be synchronized to other devices, e.g. ADC, DAC, when OSCout0/1 is used?
Thank you.
Yifei
