11 Types of PCB Interface

Author: Release time:2023-07-28 Source: Font: Big Middle Small View count:322

As we all know, there may be some problems when the various sub-modules of the circuit system perform data exchange, resulting in the inability to transmit signals normally and with high quality. For example, there is a deviation in the working timing between the circuit sub-modules (for example, CPU and peripherals), or the respective signal types are inconsistent (for example, a sensor detects a light signal). In order to solve these problems, we need to consider the corresponding interface method to deal with.


RS-485 interface

TTL level interface

CMOS level interface

SPI (Serial Peripheral Interface) 

ECL level interface

RS-232 level interface

Differential balanced level interface

CAN (Controller Area Network) interface 

Optical isolation interface

Coil Coupling Interface

I2C (Inter-Integrated Circuit) interface


What is a PCB interface

What are interfaces used in PCB design

What is interface IC

RS-485 interface

RS-485 interface is a differential serial interface, which has longer distance communication and better anti-interference ability, and is widely used in industrial fields. It is an upgraded version of the RS-232 interface, suitable for transmitting data and control signals in complex industrial environments.

The RS-485 interface is capable of longer-distance communication, and the transmission distance can reach several kilometers, which makes it very suitable for communication between distributed devices in industrial control systems.

RS-485 uses two mutually opposite signal lines for differential transmission, and the receiving end decodes the difference between the two signals, thereby effectively canceling the common-mode interference on the transmission line and greatly improving the reliability of the signal.

RS-485 supports multi-node communication and can connect multiple devices to communicate on the same bus, which makes it very suitable for complex industrial systems that require data transmission and control between multiple devices.

RS-485 is a half-duplex communication protocol, that is, each node can send and receive data, but not at the same time. This protocol is suitable for most applications in industrial control systems, where nodes often need to alternately send and receive data.

RS-485 supports different transmission rates, usually up to tens of kbps or higher. This makes it suitable for real-time applications requiring high-speed data transmission, such as monitoring systems and data acquisition systems.

The RS-485 interface uses two signal lines for differential transmission, which makes the wiring of the leads relatively simple and reduces the cost and maintenance difficulty of the system.

TTL level interface.png

TTL level interface

TTL level interface is a common and classic interface type. From the beginning of studying analog circuits and digital circuits in college, we cannot do without dealing with TTL level interfaces. For general circuit design, TTL level interface undoubtedly plays an important role. However, it also faces some limitations. First of all, its speed is generally limited within 30MHz. This is due to the fact that there are several pF input capacitors at the input of the BJT, forming a low-pass filter, which leads to the loss of high-frequency signals. In addition, the driving capability of the TTL level interface is generally a maximum of tens of milliamperes. In addition, the signal voltage during normal operation is generally high, and when it is close to an ECL circuit with a low signal voltage, it may cause obvious crosstalk problems.

CMOS level interface

We are no strangers to CMOS level interfaces, so we won't go into detail about the semiconductor characteristics of CMOS. As we all know, the power consumption and anti-interference ability of CMOS under normal conditions are much better than that of TTL interface. However, what few people know is that at high switching frequencies, the CMOS family actually consumes more power than TTL. The reasons for this require an in-depth understanding of semiconductor physics theory.

Since the current working voltage of CMOS can be reduced to a very small level, and even some FPGA cores have a working voltage close to 1.5V, which leads to a much smaller noise margin between levels than TTL, so it is easier to cause voltage fluctuations due to voltage fluctuations. Signal judgment error. The input impedance of the CMOS circuit is very high, so the capacity of its coupling capacitor can be reduced accordingly, and there is no need to use a large-capacity electrolytic capacitor.

Although CMOS circuits generally have weaker drive capabilities, TTL conversion must be performed before driving ECL circuits. When designing CMOS interface circuits, care should be taken to avoid heavy capacitive loads, otherwise the rise time will be slowed down and power consumption of the driving device will be increased (because capacitive loads do not consume power).

SPI (Serial Peripheral Interface) 

SPI (Serial Peripheral Interface) is a synchronous serial interface used to communicate with peripheral devices such as sensors, displays, and memory chips. It is a simple yet efficient communication protocol widely used in many embedded systems and electronic devices.

The SPI interface uses synchronous communication and consists of a master device (usually a microcontroller or processor) and one or more slave devices. As the leader of communication, the master device transmits data with the slave device through clock signal and data line.

The SPI interface supports the connection of multiple slave devices, and each slave device communicates with the master device through an independent chip select signal (Chip Select). This structure makes it possible to connect multiple peripheral devices on a single bus, improving the scalability of the system.

The SPI interface usually supports high-speed data transmission, and the rate can reach hundreds of kbps to several Mbps, or even higher. This makes SPI useful in applications that require fast data transfers, such as graphics displays, high-performance memory chips, and more.

The SPI interface only requires a small number of pins and a simple hardware structure, so it is very suitable for resource-constrained embedded systems. Its implementation is relatively simple, which helps reduce system cost and design complexity.

The SPI interface allows bi-directional data transfer, the master device can send and receive data at the same time. This characteristic makes SPI ideal for reading and writing data to and from memory devices such as EEPROM and flash memory.

The timing of the SPI interface is relatively flexible, and the clock polarity and phase of the communication protocol can be configured, allowing compatibility with different types of peripheral devices.

ECL level interface

The ECL level interface can be described as an old friend in the computer system! Its speed can be described as fast, and can even reach hundreds of MHz! This is due to the fact that the BJT inside the ECL is not in a saturated state when it is turned on, thereby reducing the turn-on and turn-off time of the BJT and improving the working speed. However, such high-speed performance comes at a price! Its fatal shortcoming is that it consumes a lot of power! At the same time, it also caused EMI problems, and the anti-interference ability was not excellent. If someone can strike a balance between these two factors, then he or she will surely achieve great success. In addition, it is worth noting that a general ECL integrated circuit needs a negative power supply to make its output voltage negative, so a special level shifting circuit is required.

RS-232 level interface

The RS-232 level interface is familiar to almost everyone involved in the field of electronic technology. This is a low-speed serial communication interface standard, and its level standard is indeed somewhat "abnormal": the high level is -12V, and the low level is +12V. Therefore, when we try to communicate with peripherals through the computer, a level conversion chip MAX232 is essential. However, the RS-232 interface has some disadvantages, such as slow data transmission speed and short transmission distance.

Differential balanced level interface.png

Differential balanced level interface

A differential balanced level interface represents a signal by the relative output voltage (uA-uB) of a pair of terminals A and B. Typically, this differential signal experiences a complex noise environment during signal transmission, resulting in essentially the same amount of noise on both lines. At the receiving end, the differential interface can cancel the energy of the noise, thus achieving longer distance and higher rate transmission. This feature makes the differential balanced interface widely used in industry, among which the RS-485 interface adopts the differential transmission mode, which has excellent anti-common mode interference ability.

CAN (Controller Area Network) interface 

The CAN (Controller Area Network) interface is a powerful and widely used serial communication protocol in the automotive and industrial fields. It is an advanced bus communication protocol that provides support for efficient and reliable communication of multiple devices on a network.

The CAN interface is designed to cope with harsh environmental conditions in the automotive and industrial fields, such as high temperature, high humidity, strong electromagnetic interference, etc. It has high reliability and stability, and can continue to operate stably in harsh working environments.

The CAN interface supports multi-node communication, and can connect a large number of sensors, actuators, control units and other devices to communicate on a CAN bus. This simplifies system connection, saves wiring costs, and improves system scalability.

The CAN interface is widely used in the automotive industry as an important communication protocol for modern vehicles. In automobiles, the CAN bus is used to transmit data and signals between various components of the vehicle (such as engine, braking system, air conditioning system, etc.) to achieve efficient collaborative work. In addition, the CAN interface is also widely used in the field of industrial automation and control to connect industrial equipment and systems to improve production efficiency and control accuracy.

The CAN interface adopts the communication mechanism of CSMA/CR (Carrier Sense Multiple Access with Collision Resolution), which effectively solves the conflict problem when multiple nodes send data at the same time, ensuring the integrity and accuracy of the data. This enables the CAN interface to operate efficiently in complex multi-node communication environments.

The CAN interface supports higher data transfer rates, usually with options of hundreds of kbps or several megabps. This makes it suitable for applications that need to transfer large amounts of data quickly, such as advanced driver assistance systems (ADAS) and in-vehicle entertainment systems.

There are two main versions of the CAN interface, CAN 2.0A and CAN 2.0B, and there are also some derived standards. This makes devices from different manufacturers compatible with each other, enhancing the flexibility and interoperability of the system.

Optical isolation interface

The optical isolation interface uses optical signals as the medium to realize the coupling and transmission of electrical signals. Its unique advantage is that it can be electrically isolated and therefore has excellent immunity to interference. Under high-frequency conditions, high-speed photoelectric isolation interface circuits become the first choice to meet data transmission requirements. Sometimes in order to achieve high voltage and high current control, we must design and use an optically isolated interface circuit to connect the previously mentioned low-level, low-current TTL or CMOS circuit. The input circuit and output circuit of the optical isolation interface can withstand a high voltage of several thousand volts, which is sufficient to meet general application requirements. At the same time, it is worth noting that the input part and output part of the optical isolation interface must use independent power supplies, otherwise it will cause electrical contact and lose the effect of isolation.

Coil Coupling Interface

Coil-coupled interfaces have good electrical isolation, but their signal bandwidth is limited. For example, the power transfer efficiency of the transformer-coupled interface is very high, and the output power is close to the input power. Therefore, for a step-up transformer, it can provide a higher output voltage, but only a lower current.

In addition, the high-frequency and low-frequency characteristics of the transformer are not ideal, and its main feature is to realize impedance transformation. When matched properly, the load can get enough power. Therefore, in the power amplifier circuit design, the transformer coupling interface is widely used.

I2C (Inter-Integrated Circuit) interface

I2C (Inter-Integrated Circuit) interface is a two-wire serial communication interface, often used to connect multiple devices on the same bus. It is a communication protocol widely used in electronic devices and embedded systems, and is known as "IC" or "IC".

The I2C interface requires only two wires for communication, one is the clock line (SCL) and the other is the data line (SDA). This simple two-wire structure makes I2C ideal for resource-constrained systems and on-board communication.

The I2C interface allows multiple devices to share communication resources on the same bus, and each device is identified by a unique address. This structure makes it easy to connect multiple devices in the system while saving system resources and PCB space.

I2C communication adopts a master-slave mode with an acknowledgment (ACK) mechanism. After the master device sends data, each slave device will return an acknowledgment signal. This ensures reliability and accuracy of data transmission.

The I2C interface supports different communication rates, common ones are standard mode (100 kbps), fast mode (400 kbps) and high-speed mode (3.4 Mbps). This allows I2C to adapt to the communication needs of different applications.

The I2C communication protocol is designed with low power consumption in mind, so it is widely used in low power consumption devices and sensor nodes in embedded systems.

The flexibility of the I2C interface is reflected in the address configuration and data format, which can be configured and customized according to the requirements of different devices.

The I2C interface is widely used in many fields, including consumer electronics, industrial automation, communication equipment, and automotive electronics. It is commonly used to connect various peripheral devices such as temperature sensors, pressure sensors, memory chips, digitizers, etc.

What is a PCB interface.png


What is a PCB interface?

A PCB (Printed Circuit Board) interface is a connection or interface point on a PCB that allows communication, data exchange, or power transfer between different components, devices, or subsystems on the board. It acts as a conduit for electrical signals, data, and power to flow between the various components of an electronic system, enabling them to work together.

What are interfaces used in PCB design?

Ethernet, HDMI, Thunderbolt, SATA, USB, PCI Express or other high speed interfaces 

What is interface IC?

An interface IC (Integrated Circuit) is a specialized semiconductor device designed to facilitate communication and data exchange between different components or systems within an electronic device. Interface ICs come in many forms and are customized for specific communication protocols and standards. They often contain built-in functions and circuitry to handle the complexities of data transmission and reception, making it easier for designers to integrate them into electronic designs. Some common types of interface ICs include:

UART (Universal Asynchronous Receiver/Transmitter) ICs

SPI (Serial Peripheral Interface) ICs

I2C (Inter-Integrated Circuit) IC

USB (Universal Serial Bus) ICs

Ethernet PHY (Physical Layer) ICs

CAN (Controller Area Network) ICs

HDMI (High Definition Multimedia Interface) IC

LVDS (Low Voltage Differential Signaling) ICs

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