Quad industrial digital input for PLC modules
The Maxim Integrated MAX14906ATM+ is a quad industrial digital input IC designed specifically for PLC digital input modules. It integrates four input channels with a wide supply range of 10V to 40V, making it suitable for 24V industrial control systems where the rail can sag or surge. The SPI interface handles configuration and diagnostic readback, so the host MCU can monitor each channel's status without extra GPIO. Packaged in a 48-TQFN (7x7) with exposed pad, it sits on a surface-mount board and requires a thermal via stitch under the pad to keep junction temperatures in check when all four channels are active.
The 10V to 40V supply covers the standard 24V industrial rail with margin for transients and brownout conditions. That range also means the part can run from a 12V or 36V auxiliary supply without a separate regulator, simplifying the power tree. The SPI interface runs at logic levels compatible with 3.3V or 5V MCUs — the datasheet typical threshold is 0.3×VDD, so a 3.3V master drives it cleanly. For a BOM engineer, this eliminates the need for level shifters on the control bus.