ICS8533I-01 Datasheet, PDF (11/17 Pages) Integrated Device Technology – DIFFERENTIAL-TO-3.3V LVPECL FANOUT BUFFER 3.3V operating supply

ICS8533I-01
LOW SKEW, 1-TO-4
DIFFERENTIAL-TO-3.3V LVPECL FANOUT BUFFER
TERMINATION FOR LVPECL OUTPUTS
The clock layout topology shown below is a typical termina-
tion for LVPECL outputs. The two different layouts mentioned
are recommended only as guidelines.
FOUT and nFOUT are low impedance follower outputs that
generate ECL/LVPECL compatible outputs. Therefore, termi-
nating resistors (DC current path to ground) or current sources
must be used for functionality. These outputs are designed to
drive 50Ω transmission lines. Matched impedance techniques
should be used to maximize operating frequency and mini-
mize signal distortion. Figures 5A and 5B show two different
layouts which are recommended only as guidelines. Other
suitable clock layouts may exist and it would be recommended
that the board designers simulate to guarantee compatibility
across all printed circuit and clock component process varia-
tions.
Z_o = 50Ω
FOUT
FIN
Z_o = 50Ω
50Ω
RTT =
1
((V_OH + V_OL) / (V_CC – 2)) – 2
Z_o
50Ω
V_CC - 2V
RTT
FOUT
3.3V
125Ω
125Ω
Z_o = 50Ω
FIN
Z_o = 50Ω
84Ω
84Ω
FIGURE 5A. LVPECL OUTPUT TERMINATION
FIGURE 5B. LVPECL OUTPUT TERMINATION
8533AGI-01
11
REV. A DECEMBER 6, 2007