LMX2594: Reference Clock High/Low Thresholds and SYNC timing

Josh Merti

Part Number: LMX2594
Other Parts Discussed in Thread: LMX2694-EP

In order to use the device in Category 3 SYNC the SYNC pulse needs to arrive "away from the rising edge of the OSCin signal." I had interpreted that to mean it needed to arrive after the hold time (2ns) once a OSCin rising edge was detected. At what OSCin voltage level does the LMX register a rising edge? Is my 2ns interpretation accurate? If not, what is the required SYNC timing "away from the rising edge of the OSCin signal" and what would the backoff need to be from the next OSCin rising edge?

9 days ago

0 vicente flores prado 9 days ago

TI__Genius 13201 points

Hello Josh,
Refer to snippet regarding min and max values for Sync pin:

For example the way this works is if you have a 100MHz signal a valid PSYNC window is 10ns - 2.5ns (setup time) -2ns (hold time) = 5.5ns

Your interpretation is correct as this should occur after the rising edge is detected.

Regards,

Vicente

0 Josh Merti 9 days ago in reply to vicente flores prado

Prodigy 180 points

Thank you for the reply and confirming my timing was correct. I'm still looking for the level where the rising edge of the OSCin clock is detected. I don't know where to reference the hold and setup times. For example, if the input were a 100 MHz 1.5Vp-p sine wave at what voltage would the LMX determine a rising edge of the OSCin clock had occurred?

0 Noel Fung 9 days ago in reply to Josh Merti

TI__Guru* 81900 points

Hi Josh,

Here is the timing diagram, hope it helps. You can find this diagram in LMX2694-EP datasheet.

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LMX2594: Reference Clock High/Low Thresholds and SYNC timing