VSC8115
Data Sheet
High-Speed Outputs
The high-speed output buffers, DATAOUT and CLKOUT , can be terminated as either LVDS or LVPECL outputs.
If used as LVDS outputs, the transmission lines should be routed with 100 differential impedance and need to be
terminated at the receive end with a 100 resistor across the differential pair. If used as LVPECL outputs the
transmission line should be 50 terminated, with 50 pull-down resistors near the receiving end. See Figure 4 and
Figure 5.
VSC8115
100
Figure 4. High-Speed Outputs—LVDS Termination
DC-Coupled
VDD -2.0V
VSC8115
Receiver
R
50
1
R
50
2
VDD -2.0V
Creates 2V bias
when VDD = 3.3V
AC-Coupled
VDD
Receiver
(unbiased with no
internal termination)
VSC8115
R
82
1
CIN
VDD
R
124
R
168
2
5
R
82
3
CIN
VSS
R
124
R
168
4
6
VSS
Receiver
VSC8115
CIN
(biased with
internal termination)
R
168
1
CIN
R
168
2
Figure 5. High-Speed Outputs—LVPECL Terminations
8 of 12
G52272, Rev 4.2
5/14/03
VITESSE [ VITESSE SEMICONDUCTOR CORPORATION ]
