Multi-channel input isolators for PLC applications

High speed, multi-channel digital isolators from Silicon Labs, are suited to programmable logic controller (PLC) applications, including industrial I/O modules, CNC machines and servo motor control.

The Si838x PLC field input isolator family is said to offer a combination of high speed channels, up to eight channels per device, bipolar input flexibility, high noise immunity and 2.5kV RMS safety isolation. The Si838x isolators are also suitable for process automation controllers used in distributed process control systems.

The single-chip devices provide eight channels of 24V digital field interface. By ‘daisy chaining’ 16 isolators in a system design, developers can create PLCs with up to 128 channels supported by an SPI port on the system’s embedded processor.

The controller interface can be eight parallel channels or a four-port SPI. Developers can configure the SPI for on-the-fly programming for custom debounce of noisy signals and for daisy chaining to support high-channel-density PLC designs.

Flexible bipolar input capability gives developers a choice of sinking or sourcing inputs. The LED emulator input circuit supports up to eight sinking or sourcing inputs in one device with no power supply required on the field side. The output interface to the controller supports low-power operation with 2.25V operation capability.

The Si838x isolators support data rates of up to 2Mbit/s, said to be essential for servo motor control.