ICS8521I Datasheet, PDF (7/14 Pages) Integrated Circuit Systems – LOW SKEW, 1-TO-9 DIFFERENTIAL-TO-HSTL FANOUT BUFFER

Integrated
Circuit
Systems, Inc.
PRELIMINARY
ICS8521I
LOW SKEW, 1-TO-9
DIFFERENTIAL-TO-HSTL FANOUT BUFFER
APPLICATION INFORMATION
WIRING THE DIFFERENTIAL INPUT TO ACCEPT SINGLE ENDED LEVELS
Figure 2 shows how the differential input can be wired to accept
single ended levels. The reference voltage V_REF = V /2 is
DD
generated by the bias resistors R1, R2 and C1. This bias circuit
should be located as close as possible to the input pin. The ratio
of R1 and R2 might need to be adjusted to position the V_REF in
the center of the input voltage swing. For example, if the input
clock swing is only 2.5V and V = 3.3V, V_REF should be 1.25V
DD
and R2/R1 = 0.609.
V_DD
CLK_IN
C1
0.1uF
R1
1K
+
V_REF
-
R2
1K
FIGURE 2. SINGLE ENDED SIGNAL DRIVING DIFFERENTIAL INPUT
RECOMMENDATIONS FOR UNUSED INPUT AND OUTPUT PINS
INPUTS:
OUTPUTS:
CLK/nCLK INPUT:
For applications not requiring the use of the differential input,
both CLK and nCLK can be left floating. Though not required,
but for additional protection, a 1kΩ resistor can be tied from
CLK to ground.
HSTL OUTPUT
All unused LVHSTL 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.
PCLK/nPCLK INPUT:
For applications not requiring the use of a differential input,
both the PCLK and nPCLK pins can be left floating. Though
not required, but for additional protection, a 1kΩ resistor can
be tied from PCLK to ground.
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.
8521BYI
www.icst.com/products/hiperclocks.html
7
REV. A NOVEMBER 17, 2005