[Introduction]CAN and 485 are both commonly used field buses in industrial communication. Doing a good job in the isolation and protection of communication buses is an important prerequisite for product reliability and stability. So how to do the isolation protection of the communication bus? There are many isolation schemes, how to choose the right one? This article has the answer for you!
1. Why should the communication bus be isolated?
At present, the external communication part of most products can be summarized as: MCU + transceiver + external bus, among which most of the commonly used MCUs are integrated with CAN or UART link layer controller. The level signal sent from the MCU is generally 5V or 3.3V. In order to achieve the purpose of connecting with the bus and remote transmission, it is often necessary to add a transceiver between the MCU and the bus, which plays the role of level conversion.
The use of bus communication will inevitably involve external communication wiring. CAN and 485 buses often require hundreds of meters of wiring. The longer the bus and the more complex the environment it passes through, the more likely it is to have communication problems. The complex and changeable electromagnetic field in the external environment will indirectly raise the potential of the bus, and static electricity, surge, short circuit, etc. will directly affect the communication line. The occurrence of the above situations may cause damage to the transceiver at light level, or cause motherboard failure at worst. Therefore, it is necessary to add isolation before connecting to the bus.
2. There are many communication bus isolation schemes, how to choose?
Communication isolation needs to take into account the impact of the isolation device on the communication signal. The current mainstream communication isolation solutions are optocouplers, capacitive couplings and magnetic couplings. Power supply isolation adopts micro-power DC/DC isolation power supply, so that there is no electrical connection between the input and output, avoiding the influence of the power supply end on the transceiver.
Specifically, isolation can be achieved in two ways: using discrete components to build or using integrated modules. As a high-quality power supplier in China, Jinshengyang has successively launched a variety of communication interface bus product solutions according to market demand, including integrated modules and self-built components, rich product lines to help you choose flexibly and meet the application needs of various industries.
3. Integrated power supply type and communication interface bus
1. “Core” level experience – R4/R5 bus isolated transceiver series
The use of discrete modules to build often involves the selection and procurement of many devices, and it is often necessary to control the consistency of materials, and the design is time-consuming and labor-intensive, and there is always concern about whether the design is reasonable, so the development cost soars.
Based on this, the isolation transceiver module integrating power isolation and digital isolation came into being. Jinshengyang launched chip-level R4/R5 series CAN&485 bus isolation transceiver products. The compact size makes it easy to apply and occupies less PCB area.
The advantages of the series are as follows:
Refinement design, integrated power solution
The R4/R5 bus IC is highly integrated and is a chip product with integrated power supply and digital isolation. Through precise design, the power isolation + signal isolation solution is realized inside the chip, which greatly saves the customer’s board space.
5000Vrms, high reliability design
When the high-voltage side equipment communicates with the low-voltage side equipment, common mode interference and isolation safety need to be considered, and high isolation is the primary consideration parameter. R4/R5 bus interface products are designed according to industry standards:
1) Based on UL1577 standard requirements, the isolation voltage is up to 5000Vrms,
2) The static electricity of the human body can reach several thousand volts or even higher, causing ESD damage to Electronic products. The electrostatic protection capability of the series products is as high as: 6kV (HBM)/±15kV (contact discharge);
3) The product also integrates a variety of protection functions, such as short-circuit protection, over-temperature protection, etc., to provide users with a more reliable design solution.
2. Isolation IC with integrated power supply – TDA51S-41HC
Isolation IC with integrated power supply, can be freely matched with IC such as 485/CAN module or ADC.
3. Communication interface bus with integrated power supply – module class
Jinshengyang module communication interface bus has a variety of different packaging forms (including potting, open board): SMD, DIP8, DIP24, and the pins are compatible with mainstream products in the market; functions include: high-speed, small size, (single/dual) Road) automatic transceiver type, integrated AC/DC power supply type, etc… to meet the needs of various industry applications.
4. Non-integrated power supply, chip-level communication interface bus
These products integrate digital isolators and signal interface ICs, which can be used with isolated power supplies to improve system reliability. The I/O port voltage range supports 3.3V and 5V microprocessors, the bus electrostatic protection capability is up to 15kV (HBM), and the communication rate is up to 1Mbps.
5. Signal interface IC/digital isolation IC
For the traditional discrete component self-build solution, Jinshengyang also prepared a dedicated CAN/485 signal interface IC and isolation IC for users. The pin to pin is compatible with international mainstream ICs. low cost requirements.
485 transceiver
CAN bus transceiver
digital isolator
6. Summary
With the increase of industry demand and technical requirements, the speed of update and iteration of related digital interface transceiver components is also increasing. On the premise of satisfying performance, Jinshengyang follows the market trend, strives to pursue high efficiency and high reliability, helps customers reduce system volume, improves system reliability, and provides worry-free and easy-to-use power products for users in different industries.
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