Datasheet

R3 R3
V
CC
I
CC
5 Meters
of CAT-5
R1 R1
V
EE
R2
V
CC
I
CC
R3 = 240 Ω
R1 = 50 Ω
R2 = 50 Ω
V
B
V
B
LVDSLV/PECL
SN65LVDS33, SN65LVDT33
SN65LVDS34, SN65LVDT34
SLLS490B –MARCH 2001–REVISED NOVEMBER 2004 www.ti.com
LVDS provide designers with another alternative. While the total exchange of ECL for LVDS may not be a design
option, designers have been able to take advantage of LVDS by implementing a small resistor divider network at
the input of the LVDS receiver. TI has taken the next step by introducing a wide common-mode LVDS receiver
(no divider network required) which can be connected directly to an ECL driver with only the termination bias
voltage required for ECL termination (V
CC
–2 V).
Figure 14 and Figure 15 show the use of an LV/PECL driver driving 5 meters of CAT-5 cable and being received
by TI's wide common-mode receiver and the resulting eye-pattern. The values for R3 are required in order to
provide a resistor path to ground for the LV/PECL driver. With no resistor divider, R1 simply needs to match the
characteristic load impedance of 50 Ω. The R2 resistor is a small value and is intended to minimize any possible
common-mode current reflections.
Figure 14. LVPECL or PECL to Remote Wide Common-Mode LVDS Receiver
Figure 15. LV/PECL to Remote SN65LVDS33 at 500 Mbps Receiver Output (CH1)
TEST CONDITIONS
• V
CC
= 3.3 V
• T
A
= 25°C (ambient temperature)
• All four channels switching simultaneously with NRZ data. Scope is pulse-triggered simultaneously with NRZ
data.
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Product Folder Link(s): SN65LVDS33 SN65LVDT33 SN65LVDS34 SN65LVDT34