Electronic Design

LVPECL/LVDS Clock Distribution Chips Conquer Metastability

Metastability, which essentially means chaotic output behavior resulting from input glitches, can be a source of system failures in clock distribution. Input glitches are inevitable in hot-swap applications. Micrel’s latest LVPECL/LVDS fanout buffers, though, prevent unwanted oscillations and maintain output stability when an input signal’s swing collapses or disappears.

The “Fail-Safe Input” (FSI) family includes the SY89467U (LVPECL) and SY89468U (LVDS) 2:1 multiplexer-input buffers with a fanout of 20. They join existing 1:2 and 1:8-fanout LVPECL and LVDS products. Each device offers a three-pin internal termination architecture that can interface to any differential signal (ac- or dc-coupled) as small as 100 mV (200 mV p-p) without the need for level shifting or termination resistor networks in the signal path.

The SY89467U outputs are 800-mV LVPECL with rise/fall times guaranteed to be less than 110 ps. For the SY89468U, outputs are LVDS-compatible with the same timing specs. Jitter performance is guaranteed to be less than 10 ps p-p over temperature and voltage.

The devices cost $6.15 in 1000-unit lots.


TAGS: Micrel
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