Industrial chip serialises eight current inputs to SPI

A current setting resistor allows it to be configured for Type 1, Type 2, or Type 3 inputs.

“Designed to reduce power, system cost, and size for programmable logic controller digital-input sub-systems, MAX22190 is a highly integrated IEC61131-2-compliant digital input device for industrial, process, and building automation applications,” said component distributor Mouser, which is stocking the part.

Field wiring is verified for proximity switches by a second threshold detector on each input. When wire-break is enabled, the Fault output is asserted and a register flag set if the input current drops below the wire-break threshold for more than 20ms. Additional diagnostics that assert Fault include: over-temperature, low 24V field supply, 24V field supply missing, and CRC communication error.

For robust operation in industrial environments, each input includes a programmable glitch filter. The filter delay on each channel can be independently programmed to one of eight values between 50μs and 20ms or filter bypass.

Inputs are protected to ±40V, and over 1kV of surge protection is provided potentially eliminating the need for up to eight external TVS diodes.

In addition to the 4pin SPI interface, there is an input called Latch for synchronising input data across multiple devices in parallel.

The filed side accepts a single 7V to 65V supply, and when powered by the field supply an integrated 3.3V LDO provides up to for external loads as well as powering internal circuits.

Alternatively, the chip can be powered from a 3.0V to 5.5V logic side supply connected to Vdd pin. For flexibility, the SPI interface operates at 3.3V or 5V logic levels as controlled by a pin.

Packaging is 5 x 5mm, and design support comes from the MAX22190 evaluation system, which includes a Digilent Pmod-compatible connector for SPI communication and a USBPMB2# adapter board for communicating with a PC.

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