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Figure 1. Isolated LVDS interface with
ADN4651 and ADuM5000

Diverse products for realiaing
isolated LVDS interfaces are
already on the market. Analog
Devices offers a very efficient and
reliable solution with its isolated
LVDS family consisting of
ADN4650, ADN4651, and
ADN4652, which supports data
rates of up to 600 Mbps and
simultaneously also corresponds to
the standard values of nonisolated
LVDS interfaces. In comparison,
standard digital isolators can reach
just 150 Mbps. Very high data
rates, despite existing isolation, are
possible thanks to the iCoupler®
many applications, they are in direct contact with technology. This involves a microelectromechanical
components connected to the power distribution systems (MEMS) reproduction of a transformer that
grid. The add-on modules are accordingly enables simple, space-saving isolation of digital
vulnerable to external events such as lightning signals.
strikes. Electrostatic discharge caused by human The LVDS family also offers very precise time
contact or internal capacitors that are suddenly characteristics, as well as extremely low jitter, also
charged, charged with reverse polarity, or known as timing jitter. Jitter describes the variations
discharged when the add-on modules are plugged in the rising and falling edges of the digital signals
in or unplugged can also lead to high transients. with respect to the ideal time reference. At high
Thus, a safely isolated interface is indispensable for data rates, low jitter is extremely important because
the system. it takes just 1.6ns to transmit one bit at 600 Mbps.
Otherwise, the connected assemblies could Any jitter in the rising or falling edges of the signals
easily be damaged or users endangered if voltage must allow the analog-to-digital converter enough
transients occur. Functionally isolated time for the actual high or low level so that
communication interfaces are also favorable for sampling can be performed correctly. For the
industrial measuring instruments because isolated ADN465x family, jitter is typically 70ps. The LVDS
interfaces offer a floating ground, for example, modules also offer two isolated LVDS channels,
between analogue-to-digital converters and which form the transmission and the reception
microcontrollers. This allows the measured signals channel in the ADN4651. The channels in the
to be isolated from influencing and interfering with ADN4652 are arranged inversely to the channels in
or influences and interference from the rest of the the ADN4651, whereas the ADN4650 only offers
application. transmission or reception channels, depending on

July 2020 • INDUSTRIAL TECHNOLOGY EXTRA! • p6