The ISO1211 and ISO1212 are isolated 24-V digital input receivers, compliant to IEC
61131-2 Type 1, 2, and 3 characteristics, suitable for programmable logic controllers (PLCs) and
motor-control digital input modules. Unlike traditional optocoupler solutions with discrete,
imprecise current limiting circuitry, the ISO121x devices provide a simple, low-power solution with
an accurate current limit to enable the design of compact and high-density I/O modules. These
devices do not require field-side power supply and are compatible with high-side or low-side
The ISO121x devices operate over the supply range of 2.25 V to 5.5 V, supporting 2.5-V,
3.3-V, and 5-V controllers. A ±60-V input tolerance with reverse polarity protection helps ensure
the input pins are protected in case of faults with negligible reverse current. These devices
support up to 4-Mbps data rates passing a minimum pulse width of 150 ns for high-speed operation.
The ISO1211 device is ideal for designs that require channel-to-channel isolation and the ISO1212
device is ideal for multichannel space-constrained designs.
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