
IDT / ICS LVCMOS/LVTTL FANOUT BUFFER
11
ICS8344AY-01 REV. C SEPTEMBER 9, 2008
ICS8344-01
LOW SKEW, 1-TO-24 DIFFERENTIAL-TO-LVCMOS/LVTTL FANOUT BUFFER
APPLICATION INFORMATION
FIGURE 1. SINGLE ENDED SIGNAL DRIVING DIFFERENTIAL INPUT
Figure 1 shows how the differential input can be wired to accept
single ended levels. The reference voltage V_REF = V
DD
/2 is
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
WIRING THE DIFFERENTIAL INPUT TO ACCEPT SINGLE ENDED LEVELS
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
DD
= 3.3V, V_REF should be 1.25V
and R2/R1 = 0.609.
V_REF
R1
1K
C1
0.1u
R2
1K
Single Ended Clock Input
CLKx
nCLKx
VDD
INPUTS:
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 1k
Ω resistor can be tied from CLK 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 1k
Ω resistor can be used.
RECOMMENDATIONS FOR UNUSED INPUT AND OUTPUT PINS
OUTPUTS:
LVCMOS OUTPUT:
All unused LVCMOS output can be left floating. There should be
no trace attached.