ICS9176-01 Datasheet, PDF (6/8 Pages) Integrated Circuit Systems – Low Skew Output Buffer

ICS9176-01
Applications
FBOUT is normally connected to FBIN to facilitate input to
output skew control. However, there is no requirement that
the external feedback connection be a direct hardwire from an
output pin to the FBIN pin. As long as the signal at FBIN is
derived directly from the FBOUT pin and maintains its fre-
quency, additional delays can be accommodated. The clock
phase of the outputs (rising edge) will be adjusted so that the
phase of FBIN and the input clock will be the same. See Figure
1 for an example.
The ICS9176-01 is also ideal for clocking multi-processor
sys-tems. The 10 outputs can be used to synchronize the
operation of CPU cache and memory banks operating at
different speeds. Figure 2 depicts a 2-CPU system in which
processors and associated peripherals are operating at 66
MHz. Each of the nine outputs operating at 66 MHz are fully
utilized to drive the appropriate CPU, cache and memory control
logic. The 33 MHz output is used to synchronize the operation
of the slower memory bank to the restart of the system.
Figure 1
In Figure 1, the propagation delay through the divide by 2
circuit is eliminated. The internal phase-locked loop will
adjust the output clock on the ICS9176-01 to ensure zero
phase delay between the FBIN and CLK signals, as a result,
the rising edge at the output of the divide by two circuit will be
aligned with the rising edge of the 66 MHz input clock. This
type of configuration can be used to eliminate propagation
delay as long as the signal at FBIN is continuous and is not
gated or conditional.
Figure 2
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