Automotive electronics single-chip solution based on mixed-signal technology

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Automotive electronics single-chip solution based on mixed-signal technology [Copy link]

As the degree of electronicization of automotive components continues to increase, automotive engineers are actively seeking advanced control and interface technology solutions in vehicle systems. At present, the space and energy used to embed these functional units in automotive systems are very limited. Automotive engineers are relying on novel high-voltage mixed-signal technologies to integrate complex - and until now incompatible - component functions onto a single chip. Now, the application of I3T high-voltage technology compatible with the 42V vehicle voltage has made it possible to integrate complex digital circuits (such as sensors), embedded microprocessors, and power circuits (such as excitation sources or switch drivers) together.



LIN bus system

Due to its relatively low cost, the LIN bus is being widely used in distributed electrical control systems in automobiles, such as controlling stepper motors and DC power supplies for power windows, adjusting rearview mirrors and headlights, or managing information collected by sensors about air temperature or seat position. The transmission byte of the LIN bus is as high as 20kbps. Based on a single master node and multiple slave nodes, the slave nodes are usually installed around transceivers, microcontrollers, sensor interfaces, or excitation drivers composed of discrete components. Recently, a microcontroller with a LIN bus asynchronous receiver and transmitter (UART) has been developed. This microcontroller can be used together with accessories that integrate other slave node modules (such as LIN bus transceivers, voltage regulators, watchdog timers, excitation drivers and sensor interfaces). At present, AMI Semiconductor (AMIS) has integrated all key slave node modules into a chip with a single function, low power consumption and standard IP module using mixed signal technology, which has taken the development of LIN bus a step further. The characteristics of this solution are: integrated

RC oscillator with an error of ≤15%;
dedicated IP module (such as DC or micro stepper motor driver);
compliance with LIN bus V1.3 protocol;
transmission rate up to 20kbps (special structural design);
low frequency transmission and reception;
low current consumption in sleep/bypass mode;
meeting potential market needs.

Figure 1 is a block diagram of the main components of a slave node integrated with LIN bus. AMIS's solution provides all the main functional modules required by the application layer and data link layer. These functional modules can be programmed with VHDL code and evaluated with the AMIS development board. They will be briefly introduced below.

Sampling Module with Digital Filter

This module samples the signal from the receiver and passes the resulting data stream through a digital filter to remove spurious transmissions that may be caused by attenuation of the LIN bus signal. As a result, the module improves the performance of the LIN protocol in harsh environments and minimizes synchronization and data sampling problems.

Synchronizer

The synchronizer module extracts the required information from the synchronization field to determine the exact sampling rate of the encoder and decoder. The module has an internal crystal oscillator and uses a technique that minimizes the rounding errors that occasionally occur in traditional UART technology. The main advantage of the synchronizer is that the LIN protocol can be implemented with a lower clock frequency. For example, a 250KHz master clock with a tolerance of 15% can be used to obtain accurate and error-free communication. In addition, the AMIS solution achieves a large range of duty cycle variations. A typical UART can achieve a duty cycle variation between 33% and 66% with zero crystal error. However, the AMIS solution can achieve a duty cycle variation between 12% and 88% and can fully adapt to crystal errors. While providing a large tolerance for physical layer parameters, it also improves electromagnetic compatibility, which has a greater impact on duty cycle.

Identifier filter and its dynamic management

The master node issues different slave instruction identifiers as needed during the initial operation and operation of the system. To this end, the slave node must contain a certain number of registers. The ROM instruction array refers to the different instructions executed in the slave node, and the corresponding identifiers are contained in the RAM or EEPROM. The address register module identifies different slave nodes on the same LIN bus, while the second ROM array identifies different slave nodes for different applications and execution processes. The identifier filter determines whether the instruction is executed based on the assigned identifier. If the identifier exists in the queue, the instruction is executed, otherwise it is not executed. Error

correction

The error identification module is in the data link layer, while the error correction is performed in the application layer. Therefore, the error amount is defined in software by the embedded microcontroller. The error correction module in the application layer contains a status register. Each error has a corresponding error flag bit, and the flag bit generates an interrupt request to the core of the microprocessor. The error flag can be cleared by performing a read operation on the status register. Each error directly interrupts the communication, resulting in a bit error to stop sending bytes. Then this frame of information is ignored and the slave node waits for the next interrupt field.

Frame Buffer

The frame buffer is another way to minimize interrupts to the microprocessor core. It works in conjunction with the identifier filter to reduce the number of interrupts to one per frame. The buffer contains 17 bytes (one identifier, eight transmit bytes, and eight receive bytes).

Core/State Machine and Application Interface AMIS offers different cores as needed. The core is connected to the LIN controller via interrupt signals and special function registers (SFRs), and the LIN controller can be seen as a peripheral device on the SFR bus. In addition to these LIN bus features, AMIS has developed an extensive library of IP modules, including 2, 2 and SAR ADC modules, delay triggers with output currents up to 0.3A, and H-bridges with output currents up to 3A, in line with similar semiconductor process technology platforms. Of course, using slave nodes is only part of the whole function, and providing them with enough power to integrate them in today's cars is the next important challenge for automotive electrical engineers.

42V Power Supply Technology Solution

In an ideal automotive power supply solution, the power level will be converted from the traditional 12V battery voltage to a 42V power supply system. In a 42V system, the power level will continue to increase. For example, if the maximum operating voltage of the system is set at 50V throughout its life cycle, the power supply voltage will reach 58V if there is an 8V maximum dynamic overvoltage. Adding a 12V external drive load pump will increase the system voltage requirement to 70V, and adding an ESD protection window will increase the system voltage to 80V. Moreover, automotive semiconductor devices must not only withstand higher voltages, but also have sufficient robustness to meet their harsh operating environments, such as the need to meet operating temperatures in the range of -40℃~+200℃. So far, the need to withstand higher voltages and meet harsh operating conditions has been a major obstacle to the application of intelligent SoC technology in 42V automotive electronic systems.

AMI Semiconductor's I3T80 is an 80V power supply intelligent module integration technology based on 0.35mm CMOS process. It meets the harsh operating conditions of 42V automotive systems. Devices developed from this technology include motor control drivers, DC-DC converters, high-precision analog circuits with bandwidth filters, and ADCs and DACs. Moreover, I3T80 can embed and integrate more than 150,000 gate circuits in total. Its communication protocol modules include PLL, USB, bus protocol controller, CAN and LIN communication controller. In addition, it also provides ROM and RAM memory

.

In new automotive electronic applications, as electronic components continue to increase, automotive designers are looking for a reasonable solution. In this way, highly integrated, high-reliability SoC solutions have emerged. This solution technology requires the ability to simplify execution steps and reduce control and interface costs between different electronic systems. AMIS's high-voltage, mixed-signal technology meets this need. It combines semiconductor solutions with dedicated IP modules to meet any standard interface communication bus (LIN, CAN) node application, while being compatible with 42V voltage level solutions.