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:
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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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 an IL716
An IL716 provides up to 6 kVrms isolation with a low-cost RS-232 driver
such as a Renesas HIN232ACBNZ-T.
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Isolated RS232
Repeater Using an IL716
Adding another RS-232 driver to the previous circuit allows a simple isolated
repeater.
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Simple Isolated I²C Interface
A three-channel isolator and some simple components allow bidirectional isolation
of I²C.
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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. The SCL section is similar as shown in the schematic using the other half of the P82B96.
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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 1-Wire Serial Bus
IL710 Isolators are ideal for isolating 1-wire serial busses because they have a high input impedance and an output enable. The top and bottom isolators in the diagram could be combined into one IL712 rather than two IL710s. IL710 and IL712 Isolators are available in MSOP packages for minimum 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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