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ADC14x250EVM: LMK04828

Part Number: ADC14X250EVM
Other Parts Discussed in Thread: TSW16DX370EVM, LMK04828, CODELOADER, ADC14X250,


I am working with the ADC14x250 and associated configuration GUI tool (TSW16DX370EVM GUI) to study the configuration, operation and performance of the LMK04828 JESD204B clock conditioner. The GUI allows me to select one of 3 pre-defined configurations to load into the LMK04828. My  question pertains to "configuration 2" which is denoted "DEFAULT" on the soft button appearing in the MACRO CONFIG tab of the LMK04828 pane. I made all hardware modifications required as per the instructions in Users Guide (SLAU625) paragraph 5.1.1)  . I observed (with an o'scope) a 245.76 Mhz signal being present at the ADC regardless of the presence of an external clock connected to J7! (I.e. turning the signal generator on or off had no effect on the clock going to the ADC) I would not expect this to occur, I would expect that, given the description of "configuration 2"  the ADC clock to have some dependency on the external reference, and should go away or otherwise show signs of degradation when the ext ref is altered or removed.  There are no oscillators onboard my EVM, all three Y1,2,and Y3 did not come installed.  Please help me understand why this is occurring, I spent a lot of time using all tools available (including codeloader) but still don't understand why this is happening.

Thank you!