Datasheet

_
+
Main Receiver
_
+
_
+
A > B + 80 mV
B > A + 80 mV
Failsafe
Timer
Failsafe
Output
Buffer
Reset
Window Comparator
A
B
R
SN65LVDS33, SN65LVDT33
SN65LVDS34, SN65LVDT34
www.ti.com SLLS490B –MARCH 2001–REVISED NOVEMBER 2004
RELATED INFORMATION
IBIS modeling is available for this device. Contact the local TI sales office or the TI Web site at www.ti.com for
more information.
For more application guidelines, see the following documents:
• Low-Voltage Differential Signalling Design Notes (SLLA014)
• Interface Circuits for TIA/EIA-644 (LVDS) (SLLA038)
• Reducing EMI With LVDS (SLLA030)
• Slew Rate Control of LVDS Circuits (SLLA034)
• Using an LVDS Receiver With RS-422 Data (SLLA031)
• Evaluating the LVDS EVM (SLLA033)
ACTIVE FAILSAFE FEATURE
A differential line receiver commonly has a failsafe circuit to prevent it from switching on input noise. Current
LVDS failsafe solutions require either external components with subsequent reductions in signal quality or
integrated solutions with limited application. This family of receivers has a new integrated failsafe that solves the
limitations seen in present solutions. A detailed theory of operation is presented in application note The Active
Failsafe Feature of the SN65LVDS32B, (SLLA082A).
The following figure shows one receiver channel with active failsafe. It consists of a main receiver that can
respond to a high-speed input differential signal. Also connected to the input pair are two failsafe receivers that
form a window comparator. The window comparator has a much slower response than the main receiver and it
detects when the input differential falls below 80 mV. A 600-ns failsafe timer filters the window comparator
outputs. When failsafe is asserted, the failsafe logic drives the main receiver output to logic high.
Figure 13. Receiver With Active Failsafe
ECL/PECL-TO-LVTTL CONVERSION WITH TI's LVDS RECEIVER
The various versions of emitter-coupled logic (i.e., ECL, PECL and LVPECL) are often the physical layer of
choice for system designers. Designers know of the established technology and that it is capable of high-speed
data transmission. In the past, system requirements often forced the selection of ECL. Now technologies like
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Product Folder Link(s): SN65LVDS33 SN65LVDT33 SN65LVDS34 SN65LVDT34