AC Timing Diagrams (Continued)
10007325
C — Setup and Hold Time (Internal data sampling window) defined by RSPOS (receiver input strobe position) min and max
TPPOS — Transmitter output pulse position (min and max)
RSKM ≥ Cable Skew (type, length) + LVDS Source Clock Jitter (cycle to cycle) + ISI (Inter-symbol interference)
j
j
j
Cable Skew — typically 10 ps to 40 ps per foot, media dependent
TJCC — Cycle-to-cycle LVDS Output jitter (TJCC) is less than 100 ps (worse case estimate).
ISI is dependent on interconnect length; may be zero
See Applications Informations section for more details.
FIGURE 12. Receiver Skew Margin
10007329
C — Setup and Hold Time (Internal data sampling window) defined by Rspos (receiver input strobe position) min and max
RSKMD ≥ TPPOSvariance (d) + TJCC (output jitter)(f) + ISI (m)
j
j
j
d = Tppos — Transmitter output pulse position (min and max)
f = TJCC — Cycle-to-cycle LVDS Output jitter (TJCC) is less than 100 ps (worse case estimate).
m = extra margin - assigned to ISI in long cable applications
See Applications Informations section for more details.
FIGURE 13. Receiver Skew Margin (RSKMD) with DESKEW
11
www.national.com
NSC [ National Semiconductor ]
