THVD4421 is a highly integrated and robust multiprotocol transceiver supporting RS-232, RS-422 and RS-485 physical layers. The device has two transmitters and two receivers to enable 2T2R RS-232 port. The device also integrates one transmitter and one receiver to enable half and full duplex RS-485 port. MODE selection pins enable shared bus and logic pins for the protocols to share a common single connector. Integrated termination for RS-485 bus pins and for RS-232 receiver inputs is provided so no external components are needed to realize a fully-functional communication port. These devices have slew rate select feature that enables them to be used at two maximum speeds based on the SLR pin setting. These devices feature integrated Level 4 IEC ESD protection, eliminating the need for external system-level protection components. Diagnostic loopback mode for RS-232 is provided to check for logic to bus and bus to logic path functional integrity and check for cable or connector shorts. In addition, the RS-485 receiver fail-safe feature drives logic high on received logic output when the bus inputs are open or shorted together or when the bus is idle. Shutdown mode consumes ultra-low current (10µA typical) suited for power-sensitive applications. The device needs 3V to 5.5V supply that powers the charge pump for RS-232 and the drivers and receivers for both RS-232 and RS-485. A separate logic supply VIO (1.65V to 5.5V) enables interface with low level microcontrollers.