It's time to change! Awesome change, the latest design to replace RS-485 optocoupler isolation
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This post was last edited by Jacktang on 2019-4-12 09:05 Friends who have worked on RS-485 optocoupler isolation circuits must have been annoyed for a long time. This commonly used circuit often occupies a large area in the circuit board PCB. Especially when designing a relatively small product circuit board, you have to reserve a piece of space for this part of the circuit. I have long had the urge to make this part of the circuit smaller, but I can say that I have been holding back for a long time... A few days ago, I saw someone in my circle of friends recommending TI's latest solution for isolated RS-485 transceivers. It was really exciting. The official announcement stated: The same type of RS-485 transceiver design, PCB areaReduce up to 85% of board space and up to 50% of board space compared to the industry standard 16-pin SOIC package. [font=-apple-system-font, BlinkMacSystemFont, Helvetica Neue, PingFang SC, Hiragino Sans GB, Microsoft YaHei UI, Microsoft YaHei, Arial, The official name of the solution is ISO1500 isolated RS-485 transceiver (查看详情), and its schematic diagram is as follows: About the circuit of isolated RS-485 transceiver, the volume and component BOM number of several solutions are compared: [attach]409363 [/attach] (A) is a commonly used optocoupler solution circuit, (B) is a 16-pin SOIC isolated RS-485 transceiver circuit, (C) is the Texas Instruments ISO1500 IC circuit Usually, those of us who have done RS-485 isolation know that optocouplers are generally used to achieve RS-485 system current isolation, which generally requires 3 optocouplers, two high-speed optocouplers (one for sending and receiving signals) and one low-speed optocoupler for direction control. This solution also requires a large number of external components, including Schmitt buffers, Schmitt triggers, resistors and bypass capacitors. The following is a typical isolated RS-485 design using optocouplers as shown below: The commonly used isolated RS-485 generally uses three optocouplers and a bunch of peripheral components, which not only increases the cost but also increases the circuit board area. The product volume requirements are getting smaller and smaller, and the smaller volume also adds enhanced functions. In addition, the trend of small packaging of SMD devices, the circuit board space limitations sometimes make it necessary to simplify the conventional circuit design. In the heating, ventilation and air conditioning (HVAC) system that regulates the temperature and airflow in the building, the HVAC control board that requires RS-485 interface isolation needs to be able to combine advanced monitoring and interface with the intelligent constant temperature system. Customers and bosses don't like to make the product volume very large. The more commonly used RS-485 is a common communication interface in these systems because of its long-distance reliability. When RS-485 nodes are placed in locations with different ground potentials, common-mode noise can cause communication failures, and isolation is required to prevent these ground potential differences. Using bulky optocoupler solutions to isolate RS-485 has left us with compromises in other areas of the system. The trend is for isolation interfaces to be small and compact, and one IC can do it all. The ISO1500 is an isolated RS-485 transceiver integrated IC. It's time to change! Awe-inspiring change, replacing the latest design of RS-485 optocoupler isolation,,,, ISO1500 Chinese information
iso1500.pdf
(2.3 MB, downloads: 26)
The official website provides an evaluation board design reference Evaluation board data
sllu290.pdf
(1.11 MB, downloads: 30)
Friends who like it, please tell us your ideas
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