Texas Instruments' ISO1211 and ISO1212 devices are isolated 24 V to 60 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 configurable as sourcing or sinking inputs.

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.

The ISO121x devices reduce component count, simplify system design, and reduce board temperatures compared to traditional solutions. For details, refer to TI's Technote How To Simplify Isolated 24 V PLC Digital Input Module Designs.