Dear colleague,
A customer use LMH6644 to shift Serial TX and RX signal. The schematic is below，RO&RI is RX signal，CO&CI is TX signal. Vsupply+ - Vsupply- = 5.5V.
RO&RI test result:
RO is yellow curve and LMH6644 D channel input and RI is green curve and LMH6644 D channel input.
And input RO high level holding time is 507ns, but output RI rise time delays 29ns, decrease time delays 9ns.
So high level holding time becomes shorter. Customer want keep the length of high level time consistent.
But CO&CI test result didn't has this problem as below:
CO is yellow curve and LMH6644 C channel input and CI is green curve and LMH6644 C channel input. The red label is inverted in the figure.
So
1. Why does this happen? The difference between the two test circuits is connection of LOW_LEVEL and HIGH_LEVEL.
2. How to solve this problem? Customer want keep the length of high level time consistent.
Best Regards,
Rock Su
