Separated USB to RS-485 Converter with Overvoltage Protection

USB-485/So is a product that converts a USB port into a isolated interface, allowing for the connection of an RS-485 communication bus to a PC.

The FTDI chip used emulates a standard COM port on the computer, which is then converted inside the converter into a differential signal, compliant with the RS-485 standard. The low-impedance RS-485 drivers allow for the connection of up to 128 devices in a network - as long as they also use low-impedance drivers.

The product is equipped with galvanic isolation of the RS-485 port at a level of 1kV DC and highly effective surge protection of 600A @ 8/20μs. The effectiveness of the surge protection is increased by the use of a resettable MOSFET fuse.

The product is designed for use in industrial conditions, where there are many dangerous surges and potential differences, while also requiring high reliability.

It is dedicated for use with industrial buses and protocols, commonly used in PLC or BMS controllers. The protections and isolation not only protect the product from damage, but also protect the USB port on the computer. To ensure proper functioning of the surge protection in USB-485, it is necessary to ground the computer's casing.

USB-485/So has switchable Pull-Up / Pull-Down resistors (factory default) with a value of 560Ω for lines A and B. The resistors can be turned off by opening the housing and removing the jumpers on the PCB board.

Internal structure of the USB-485/So converter

RS-485 port connection

Network structure using USB-485

Technical specifications: