ics527-02 Integrated Device Technology, ics527-02 Datasheet - Page 3

• Manufacturer Part Number: ics527-02
• Description: Clock Slicer User Configurable Pecl Input Zero Delay Buffer
• Manufacturer: Integrated Device Technology

IDT™ / ICS™ CLOCK SLICER USER CONFIGURABLE PECL INPUT ZERO DELAY BUFFER 3
ICS527-02
CLOCK SLICER USER CONFIGURABLE PECL INPUT ZERO DELAY BUFFER
External Components
Decoupling Capacitors
As with any high performance mixed-signal IC, the
ICS527-02 must be isolated from system power supply
noise to perform optimally.
Decoupling capacitors of 0.01µF must be connected
between each VDD and the PCB ground plane. The
capacitor must be connected close to the device to
minimize lead inductance.
Series Termination Resistor
Clock output traces over one inch should use series
termination. To series terminate a 50 trace (a
commonly used trace impedance), place a 33 resistor
in series with the clock line, as close to the clock output
pin as possible. The nominal impedance of the clock
output is 20 .
Using the ICS527-02 Clock Slicer
First use DIV2 to select the function of the CLK2 output.
If DIV2 is high, a divide by 2, low skew version of CLK1
is present on CLK2. If DIV2 is low, a SYNC pulse is
generated on CLK2. The SYNC pulse goes high
synchronously with the rising edges of PECLIN and
CLK1 that are de-skewed. The SYNC function operates
at CLK1 frequencies up to 66 MHz. If neither CLK1/2 or
a SYNC pulse are required, then CLK2 should be
disabled by connecting OECLK2 to ground. This will
also give the lowest jitter on CLK1.
Next, the feedback scheme should be chosen. If CLK2
is being used as a SYNC pulse, or is tri-stated, then
CLK1 must be connected to FBIN. If CLK2 is selected
to be CLK1/2 (DIV2=1, OECLK2=1) then either CLK1 or
CLK2 must be connected to FBIN. The choice between
CLK1 or CLK2 is illustrated by the following examples
where the device has been configured to generate
CLK1 that is twice the frequency on PECLIN.
Using CLK1 as feedback will always result in
synchronized rising edges between PECLIN and CLK1
if CLK1 is used as feedback. CLK2 could be a falling
edge compared to PECLIN. Therefore, wherever
possible it is recommended to use CLK2 for feedback,
which will synchronize the rising edges of all three
clocks.
More complicated feedback schemes can be used,
such as incorporating multiple output buffers in the
feedback path. An example is given later in the
datasheet. The fundamental property of the ICS527-02
is that it aligns rising edges on PECLIN and FBIN at a
ratio determined by the reference and feedback
dividers.
Set S1 and S0 (page 2) based on the output frequency.
Lastly, the divider settings should be selected. This is
described in the following section.
Determining ICS527-02 Divider Settings
The user has full control in setting the desired output
clock over the range shown in the table on page 2. The
user should connect the divider select input pins directly
to ground (or VDD, although this is not required
in d e t e r m in a te
P E C L IN
P E C L IN
P E C L I N
P E C L I N
p h a s e is
C L K 1
C L K 2
C L K 1
C L K 2
PECL ZDB AND MULTIPLIER/DIVIDER
C L K 2 F e e d b a c k
C L K 1 F e e d b a c k
ICS527-02
REV H 092209