The MAX13487E evaluation kit (EV kit) is a fully assembled and tested PCB that contains a half-duplex RS-485/RS-422 AutoDirection-controlled transceiver with ESD protection. The EV kit circuit features a differential driver and receiver. The circuit’s receiver is a 1/4-unit load for the RS-485 bus and can communicate up to 500kbps. The MAX13487E AutoDirection and reduced-driver slew-rate features are demonstrated on the EV kit circuit. The EV kit can also be used to evaluate the MAX13488E IC, which can communicate up to 16Mbps.
Power for the transceiver circuit is provided by a MAX256 H-bridge DC/DC converter, which powers the isolated section of the MAX13487E RS-485/RS-422 circuit. Input-ripple current and radiated noise are minimized by using an H-bridge design. The isolated H-bridge DC-DC converter operates at 420kHz. Input power to the EV kit circuit can be supplied by a +5V DC source.
The DC-DC converter circuit uses a surface-mount transformer to provide galvanic isolation and a full-wave rectifier, and provides a regulated +5V to the MAX13487E. A MAX1659 linear low dropout (LDO) regulator provides the regulated output and up to 300mA of current. The output current limit and thermal shutdown provide for a robust isolated RS-485/RS-422 transceiver circuit and power supply. The transceiver and power circuits and PCB are designed for 2500VRMS isolation.
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