UMW ST3485EBDR(UMW)

UMW ST3485E is a half-duplex, low-power RS-485 transceiver powered by 3.3V, fully compliant with TIA/EIA-485 standard requirements. The UMW ST3485E contains one driver and one receiver, both of which can be independently enabled and disabled. When both are disabled, the driver and receiver outputs enter a high-impedance state. The UMW ST3485E features 1/8 unit load, allowing up to 256 ST3485E transceivers to be connected to the same communication bus. Error-free data transmission at up to 12Mbps is achievable. The UMW ST3485E operates over a supply voltage range of 3.0 to 3.6V, with fault protection, over-temperature protection, current limiting protection, and overvoltage protection.

The UMW ST3485EBDR is a half-duplex, high-speed transceiver for RS-485/RS-422 communications, containing one driver and one receiver. It features fault protection, overvoltage protection, and overcurrent protection. The MAX3485E enables error-free data transmission at rates up to 12Mbps. Standard RS-485 receiver input impedance is 12kΩ (1 unit load), and a standard driver can drive up to 32 unit loads. The UMW ST3485EBDR transceiver's receiver features 1/8 unit load receiver input impedance (96kΩ), allowing up to 256 transceivers to be connected in parallel on a single bus. These devices may be used in any combination, or combined with other RS-485 transceivers, provided the total load does not exceed 32 units. Two mechanisms are employed to prevent excessive output current and power dissipation caused by fault conditions or bus contention. First, overcurrent protection provides fast short-circuit protection across the entire common-mode voltage range (refer to Typical Operating Characteristics). Second, when die temperature exceeds 140°C, the thermal shutdown circuit forces the driver outputs into a high-impedance state.

• 3.3V supply, half-duplex
• 1/8 unit load, supports up to 256 devices on bus
• Driver output short-circuit protection
• Over-temperature protection
• Low-power shutdown
• Receiver open-circuit protection
• High noise immunity
• Integrated transient voltage suppression
• Data rate up to 12Mbps in electrically noisy environments
• SOP-8 package

• Bus Networking: The MAX3485E RS485 transceiver is designed for bidirectional data communication on multipoint bus transmission lines. These devices can also be used as line repeaters for cable lengths exceeding 4000 feet. To minimize reflections, the transmission line should be terminated at both ends with its characteristic impedance, and branch lines other than the main line should be kept as short as possible.
• Daisy-Chain Networking: Also known as daisy-chain topology, this is the standard and recommended RS485 bus wiring topology by organizations such as TIA. The wiring method connects a master control device and multiple slave devices in a daisy-chain configuration. This approach has no branches, offering the advantages of minimal signal reflections and high communication reliability.
• Bus Port Protection: In harsh environments, RS485 communication ports typically require protection against ESD, lightning strikes, and surges, and may even need to withstand 380V power input to prevent damage to smart meters and industrial control hosts.