ICS841S02I Datasheet, PDF (12/17 Pages) Integrated Device Technology – PCI EXPRESS™ CLOCK GENERATOR

ICS841S02I
PCI EXPRESS™ CLOCK GENERATOR
PRELIMINARY
RECOMMENDATIONS FOR UNUSED INPUT AND OUTPUT PINS
INPUTS:
LVCMOS CONTROL PINS
All control pins have internal pull-ups or pull-downs; additional
resistance is not required but can be added for additional
protection. A 1kΩ resistor can be used.
OUTPUTS:
HCSL OUTPUTs
All unused HCSL outputs can be left floating. We recommend
that there is no trace attached. Both sides of the differential output
pair should either be left floating or terminated.
OUTPUT DRIVER CURRENT
The ICS841S02I outputs are HCSL current drive with the cur-
rent
being
set
with
a
resistor
from
I
REF
to
ground.
For
a
50Ω
pc
board trace, the drive current would typically be set with a R_REF
of 475Ω which products an I_REF of 2.32mA. The I_REF is multiplied
by a current mirror to an output drive of 6*2.32mA or 13.92mA.
See Figure 3 for current mirror and output drive details.
I_REF
R_REF
R_L
R_L
FIGURE 3. HCSL CURRENT MIRROR AND OUTPUT DRIVE
IDT^™ / ICS^™ PCI EXPRESS CLOCK GENERATOR
12
ICS841S02BGI REV. C NOVEMBER 1, 2007