Level conversion application of digital isolation chip
Time:2022-08-01
Views:1925
With the advent of industry 4.0, digital interconnection has become more and more common. In the interconnection of digital circuits, the interface level mismatch between devices is often encountered, such as the common 3.3V and 5V.
The level mismatch will occur when two different voltage chips communicate. If the voltage difference between the two ends of the communication is too large, it is likely to cause chip damage. Therefore, it is necessary to make the level on both sides meet the requirements of the chip through level conversion and ensure normal communication.
1. Application of bl714x in isolated multi power domain level conversion
Figure 1
In the scenario shown in Figure 1, the primary side is at 5V level and the secondary side is at 3.3V level, and both sides are not grounded together. In the isolation level conversion application of multi power domain similar to this scenario, using bl712x/bl714x series digital isolation chips to design the level conversion circuit not only has the characteristics of high transmission rate, high withstand voltage and simple peripheral device circuit, but also saves PCB space and is convenient for integration in various systems.
Bl712x/bl714x digital isolation chip has a transmission speed of up to 100Mbps, which is much higher than that of ordinary optocoupler. Unlike the optocoupler, which needs to provide bias or limit current, bl712x/bl714x digital isolation chips do not need other external components to improve performance, and only need two external VDD bypass capacitors to work.
2. Application of bl712x/bl714x in non isolated multi power domain level conversion
Figure 2
As shown in Figure 2, in the scenario of non isolated multi power domains (each power domain has the same voltage), there may be one or more power supplies in the off state and other power supplies in the working state in some occasions.
In this case, if there is any data communication link between the two power domains, the shutdown region may obtain power from the data line in a parasitic manner, resulting in incomplete shutdown or high power consumption of the whole system.
Figure 2. When the primary side is open and the secondary side is closed, electric leakage from the primary side to the secondary side will be caused; To avoid leakage current, the digital line must be set to low-level output or high impedance mode.
Figure 3
In order to avoid the above problems, it can be seen from Figure 3 that when using bl712x/bl714x Series Digital Isolators to replace the direct connection of two power domains, the leakage current between them can be blocked. Since there is no need to control the output state at this time, the protection design of hardware and software can be simplified.
Figure 4
For the application of non isolated multi power domains (the voltage of each power domain is different), there is a data link between the common ground of each power domain, and the level between each other needs to be converted, otherwise the high-voltage side and low-voltage side will leak, and each other will be burned in serious cases.
Using bl712x/bl714x Series Digital Isolators to realize level conversion under the condition of non isolation and common ground, replacing the dedicated level conversion chip can also solve the problem of high side and low measured leakage (Fig. 4).
From the above scenario description, we can see that the function of digital isolator is not limited to "isolation", and digital isolation chip is also suitable for non isolated level conversion applications. Isolation devices can be used for isolation interface, isolation drive, level conversion, etc.
The bl712x/bl714x digital isolation chip designed and produced by Shanghai belling has the advantages of smaller size, faster speed, lower power consumption and temperature range, and has higher reliability and longer life. It is more suitable for information communication, power meters, industrial control, new energy vehicles and other fields.
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