Tool/software:
Hello,
The objective I am going to propose is to find a logical explanation for the behavior of LMX2492-Q1, I hope you can help me.
I use LMX2492-Q1 in several frequency synthesizer circuits, all of them present adequate behavior according to our requirements, but I have found a scenario where the only PLL1 resets unexpectedly (losing the entire reg.memory), even though the entire system is designed so that they never turn off or reset.
In my circuit: a LMX2492-Q1 (PLL1) has the CE pin connected to LDO_3V3 through a 0 Ohm resistor. Another LMX2492-Q1 (PLL2) has the CE pin connected directly to LDO_3V3 but there is no resistor, there is simply a trace. Also POWERDOWN=00 (default) in both PLLs.
I have carefully checked the control of the PLLs, ruling out any problem that explains the unexpected reset.
The solution that I have found to this problem with PLL1 is simply "do not populate the 0 Ohm resistor".
It seems that somehow, perhaps a (transient) signal is coupled to the resistor and causes PLL1 to reset losing register memory.
Is this possible? Can you give me another explanation?
BR
