PLL LMX2491 reference clock LVDS support
PLL lmx2491 have OSCin pin to apply reference clock on it. It said it is differential. One famous differential is LVDS. It does not tell anything about it's compatible logic standards. It said:
Also it tells:
If using a differential input, this must be terminated differentially with a 100-Ω resistance and AC-coupled to the OSCin and GND/OSCin* terminals.
It seems it have to support LVDS, doesn't it?
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If using a differential input, this must be terminated differentially with a 100-Ω resistance and AC-coupled to the OSCin and GND/OSCin* terminals.It seems it have to support LVDS, doesn't it?
The chip is designed to take a differential input clock. This is clearly shown on page 1 of the datasheet:
I didn't look at the rest of the datasheet, but it seems pretty clear that the input clock is differential between OSCin and OSCin*. In the schematic above, they are driving the chip with a single-ended clock, so connected the OSCin* input to ground (AC-wise).
From this schematic and the sentence you quoted, it further seems that the chip wants about 100 Ω differential source impedance on the incoming clock. You will have to read the rest of the datasheet to see if that is correct and what details may apply.
I didn't look up the specs for LVDS to see if the chip input requirements are compatible, but they probably are.
Note that the clock inputs apparently provide their own DC bias and you may only AC-couple to them. Again, the exact requirements are surely spelled out in later sections of the datasheet.
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