BiCMOS PLL CLOCK GENERATOR
TYPICAL APPLICATIONS
S4402/S4403
The S4402/S4403 chips are designed to meet a
large variety of system clocking requirements. Sev-
eral typical applications are provided below.
Clock Outputs
at twice, equal to,
or half the
XTAL
REFCLK
S4402
Application 1. High-Frequency, Low-Skew Clock
Generation
input frequency
One of the most basic capabilities of the S4402/
S4403 devices is generating multiple phase-
aligned low-skew clocks at various multiples of the
input clock frequency. For example, in a multiple-
board system a half-frequency clock can be gener-
ated for use across the backplane, where it is
simpler to route a low-speed signal. This signal
can then be doubled on the boards, and synchro-
nization will be maintained.
Application 2. Low-Skew Clock Distribution
XTAL
REFCLK
S4402
REFCLK
One common problem in clocking high-speed sys-
tems is that of distributing several copies of a sys-
tem clock while maintaining low skew throughout
the system. The S4402/S4403 devices guarantee
low skew among all the clocks in the system, as
they have effectively zero delay between their in-
put and output signals, with an output skew of less
than 400 ps. The user can also adjust the phases
of the outputs in increments as small as 3.125 ns,
for load and trace length matching.
S4402
REFCLK
S4402
REFCLK
S4402
Application 3. Delay Compensation
REFCLK
S4402
Since the relative edges of the S4402/S4403 out-
puts can be precisely controlled, these chips can
be used to compensate for different delays due to
trace lengths or to internal chip delays, simplifying
board layout and bus timing. In the example
shown, the two ASICs have a difference of several
nanoseconds in their propagation delays. The
S4402s ensure that the output signals are aligned,
so that the data valid uncertainty on the com-
mon bus is minimized.
ASIC
Input
Clock
REFCLK
S4402
ASIC
Clock tree output
Applied Micro Circuits Corporation
6195 Lusk Blvd., San Diego, CA 92121 • (619) 450-9333
Page 7
AMCC [ APPLIED MICRO CIRCUITS CORPORATION ]
