MAX31911 Octal, Digital Input Converter / Serial

The MAX31911 industrial interface serially converts, conditions and serializes 24V digital output sensors and switches used in industrial processes that require 5V CMOS compatible signals through microcontrollers and building automation. It provides a front-end interface circuit for a programmable logic controller (PLC) digital input module.

The device has integrated current limiting, low-pass filtering, and channel serialization. The input current limit allows a significant reduction in power consumption compared to the conventional discrete resistor divider that achieves the supply from the excitation voltage. The optional on-chip low-pass filter allows flexible application based sensor output debounce and filtering. The on-chip serialization allows a drastic reduction in the number of optocouplers used for isolation. Any number of input channels can be serialized and output can only be serialized via a SPI-compatible device. Serialization is stackable. This reduces the need for only three optocouplers, regardless of the number of input channels.

Relative to high-frequency noise and fast electrical transients for enhanced robustness, a multi-bit CRC code is generated and each 8-bit data is transmitted through the SPI port. The on-chip 5V voltage regulator can be used for external power supplies, digital isolators, optocouplers or other external 5V circuits. In ultra-low power applications, Maxim offers a pin-compatible version and the MAX31910 uses patent-pending technology to achieve further Reduced power consumption, input current limit alone, anything possible. The next-generation versions of the MAX31910 and MAX31911 will include energy LED drivers while remaining pin-compatible.