What it is and where it fits
The DS26C31TMX/NOPB is a quad differential line driver from Texas Instruments, built for RS422 and RS485 communication links. It packs four drivers in a single 16-SOIC package, with no receivers on-chip — purely a transmit-side part for pushing balanced signals down a twisted pair. The 16-SOIC footprint (0.154" body width, 3.90 mm) is a common one — if your board already has a SOIC-16 land pattern for a UART or transceiver, this part drops in without a layout change.
Surface-mount 16-SOIC, 3.90 mm body width — the narrow SOIC footprint. The supplier device package is the same 16-SOIC, so no confusion on the land pattern.