Isolated Serial
Interfaces
Isolating serial interfaces reduces noise and eliminate ground loops.
But unlike optocouplers, IsoLoop isolators have unlimited life with
no degradation. Reduce board space with up to two channels per MSOP
and up to five channels in 0.15" narrow-body SOICs. Illustrative
applications are as follows:
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Applications
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Differential Signal Isolation Using an IL611
IL600-Series Isolators are ideal for isolating differential signals
because you have access to the input coils and do not need
input power to drive the signal across the barrier.
When the voltage at node Y is greater than the voltage at node Z there is a logic high at the OUT+ node and a low
on the OUT- node.
Outputs are reversed when the voltage at node Z is higher than the voltage
at node Y. Current-limiting resistors can be selected to ensure input coil
currents are at least ±5 mA and no more than ±10 ma
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Isolated
RS232 Using IL712s
IL712s provide 2.5 kVrms isolation (1 minute) and 30 kV/µs typical
common-mode transient immunity. The IL712-1 is a unique MSOP dual-channel
isolator to minimize board space.
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Isolated I²C Using IL612A
This circuit provides bidirectional isolation of I²C bus signals with no
restrictions on data rate and none of the I²C bus latch-up problems common
with other isolation circuits.
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Isolated USB UART Using an IL712
Isolating the input to a USB controller (rather than the bus lines) requires fewer isolation channels, and is therefore usually the simplest solution as shown in the following illustrative circuit:
The Microchip MCP2200 is a USB 2.0 to UART Protocol Converter. The IL712/IL721 Series are best-in-class bidirectional isolators with a remarkable 100 ps of jitter, and parts are available in unique MSOPs to reduce board space.
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Isolated USB Controller Using IL710s
The IL710’s output enable makes it ideal for bidirectional interfaces such as USB. In this illustrative circuit, the directional output (pin 27) of the PLX/NetChip NET2890 transceiver enables the isolator channels in the active direction:
The IL710 is available in a unique MSOP for five channels of isolation on minimal board space.
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Isolated I²S Using IL710/IL711
Isolating a CD transport DAC with an isolated Inter-IC Sound (I²S)
bus eliminates ground loops. The IL700-Series isolators' precision edge placement
(only 50 ps typical jitter) all but eliminates noise-induced phase error
and hum in the analog side of the audio system.
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