ADS42JB69EVM: How to apply External Clock

Hans,

I would use 0.1uF capacitors for R61 and R62 since the clock signals are self biased. If you are using subclass 1 mode, the SYSREF from the LMK must be synchronized with your external clock source. This is accomplished by taking the 10MHz reference source that is usually provided on most signal generators and connecting it to J21 of the EVM. You must install C74 and remove R19 for this mode. Another option is to synchronize the external clock to the EVM 10MHz reference clock, which is available on SMA J16. With this setup, C74 must be removed  and R19 installed.

You can use the GUI with the normal settings as you would if using the onboard clock but may want to power down the LMK output that is feeding the ADC input clock to minimize clock switching noise.

Regards,

Jim