Application of digital isolation in electronic products

In current electronic systems, there are often many digital and analog signals that need to be transmitted, and high resistance isolation characteristics are required to achieve isolation between electronic systems and users. Optocouplers, magnetic isolation, and capacitive isolation are often used to achieve this, but their power consumption, speed, isolation voltage, etc. are often not optimal. For the isolation product market, Silicon Labs has launched wireless transmission to achieve signal isolation and transmission, and has greatly improved performance.

This article will focus on the working principle, product features and performance of digital isolators, and then explain some applications of digital isolators in electronic products.

1. Working principle of isolation products

1. According to the transmission mode of isolation products, they can be divided into optocoupler isolation, magnetic isolation, capacitive isolation, and wireless isolation used in Silicon Labs products. Taking optocoupler as an example, its transmission principle is as follows:

The input electrical signal drives the light emitting diode (LED) to emit light of a certain wavelength, which is received by the photodetector to generate photocurrent, and then further amplified and output, thus completing the conversion of electricity-light-electricity, thus playing the role of input, output and isolation. Its advantages are one-way signal transmission, high isolation voltage and strong anti-interference ability; its disadvantages are also obvious, the speed is not particularly fast, the maximum is 50Mbps, the LED power consumption is large, and the LED is easy to age after a long working time.

2. Silicon Labs uses wireless methods to isolate and transmit signals. The following uses Si84xx as an example to illustrate its working principle.

Description: The left Input is used as the input of the signal. After converting the signal into a wireless RF signal, the right side receives and processes the RF signal, and outputs the received signal through the Output. The modulation frequency of the wireless signal is about 2.4GHz, which is not within the communication frequency range. Its modulation and demodulation signals are as follows:

Because wireless signals are used for signal transmission, the signal conversion and transmission speed is fast, the data transmission rate can reach 150Mbps, the size can be made very small, the power consumption is very low, the propagation time is short, and the isolation voltage is very high. Because wireless signal transmission is used, it is easy to cause electromagnetic interference.

2. Silicon Labs Isolation Product Classification and Features

1. Silicon Labs isolation products can be roughly divided into three categories: digital isolation, isolated gate-level drive, and current isolation sensing, as follows:

2. Product features. Silicon Labs isolation products have the advantages of low power consumption, high speed, and short propagation delay. They are the fastest and most integrated isolators in the industry. The maximum speed reaches 150Mbps, and one IC can integrate up to 6 channels. The isolation voltage can reach 5KV, and the common mode transient immunity (CMTI) is high, greater than 25KV/uS; in terms of EMI, it complies with IEC 61000-4-8 and IEC 61000-4-9 standards.

3. There are many digital isolation products to choose from, including unidirectional, bidirectional and mixed isolation products, as well as single-channel and multi-channel products, as shown below.

4. The isolation performance of the product is very good, and its parameters are as follows.

3. Performance and Application of Silicon Labs Isolation Products

1. Silicon Labs isolation products can eliminate ground loop problems, achieve transmission of different voltages, increase common-mode rejection ratio, etc.

A, Eliminate ground loop application

B. Realize voltage transmission application

C, increase the common mode rejection ratio application

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D, making logic level compatible with applications

2. Application of Silicon Labs isolation products in the industrial field

A, Isolate ADC data

The characteristics are transmitting low voltage signals in high voltage circuits, eliminating ground loops, suppressing common mode noise, low latency, high speed and high reliability.

B, Industrial communication isolation

It can realize the isolation of field bus, device bus and control bus, and can protect and isolate users and systems, with fast transmission speed and high reliability.

3. Silicon Labs isolation products such as Si8405 can achieve bidirectional isolation of I2C, reduce 1/3 of the space compared to optocouplers, support 35mA open-circuit output, and only require two resistors and capacitors for the peripheral circuit, supporting a clock speed of up to 1.7MHz.

In traditional I2C communication isolation, two sets of unidirectional isolation devices need to be reused to effectively isolate bidirectional signals (such as Data).

4. Application of Silicon Labs isolation products in energy systems, typically switching power supplies, lighting, inverters, motor control, etc. The application opportunities in the system are as follows:

Silicon Labs' digital isolation devices have the characteristics of high speed, high isolation voltage, low power consumption and high reliability. They can be well applied to electronic products, and there are many types of products to choose from. In the application of electronic systems, Silicon Labs' digital isolation devices can well eliminate ground loops, increase common mode rejection ratio, and isolate communication data.

Currently, Silicon Labs authorized agent Shiqiang Telecom can provide Si84xxISO development board, distributed power supply reference design, IBIS model, etc.