The Maxim Integrated MAX3140CEI+ is a UART controller with an integrated transceiver that handles both RS232 and RS485 protocols on a single chip. It communicates with the host MCU over an SPI interface and presents the serial line as a UART, so the software side sees a standard UART peripheral regardless of which physical layer is active. This makes it a compact choice for a mixed-protocol serial port — one BOM line covers both RS232 and RS485 without an external protocol-switching IC.
Supply and power — what the ratings mean
The 640 µA supply current is low enough for bus-powered RS232/RS485 ports.
It belongs in office equipment, test bench gear, indoor instrumentation, or any environment where the ambient stays above freezing and below a warm room. Not for an engine bay, a rooftop telecom cabinet, or a factory floor without climate control.
Package and rework
The MAX3140CEI+ comes in a 28-QSOP (3.90 mm body width, 0.154″ pitch). It ships in a tube.