Single-chip solution for automotive electronics based on mixed-signal technology
With the continuous improvement of the electronic level of automotive components, 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, and automotive engineers are relying on novel high-voltage mixed-signal technology to integrate complex-as yet incompatible component functions on a chip. Now, the application of I3T high-voltage technology compatible with 42V vehicle voltage can already integrate complex digital circuits (such as sensors), embedded microprocessors and power circuits (such as excitation sources or switch drivers).
Due to its relatively low cost, the LIN bus system is being widely used in the distributed electrical control system of automobiles, such as stepper motors and DC power supplies for controlling electric windows, adjusting rearview mirrors and headlights. , Or manage the information about temperature or seat location collected by sensors. The transmission byte of LIN bus is up to 20kbps. Based on the structure of a single master node and multiple slave nodes, usually, the slave node is installed around the interface of the transceiver, microcontroller, sensor or the excitation driver composed of discrete components. Recently, a microcontroller with LIN bus asynchronous transceiver (UART) has been developed. This microcontroller can be integrated with other slave node modules (such as LIN bus transceiver, voltage regulator, watchdog timer) , Excitation driver and sensor interface) are used together. At present, AMI Semiconductor (AMIS) company uses mixed-signal technology to integrate all the key slave node modules on a single chip with special functions, low power consumption, and standard IP modules, which has pushed the development of LIN bus one step further. The characteristics of the program are:
Integrated RC oscillator, error ≤15%;
Dedicated IP module (such as DC or micro stepping motor driver);
Comply with LIN bus V1.3 protocol;
Transmission rate up to 20kbps (special structural design);
Low frequency transceiver;
Low current consumption in sleep / bypass mode;
Meet the potential market demand.
Figure 1 is a block diagram of the main components of a slave node with an integrated LIN bus. The AMIS solution provides all the main functional modules required by the application layer and the data link layer. These functional modules can be programmed with VHDL code and evaluated with the AMIS development board, and they will be briefly introduced below.
Sampling module with digital filter This module collects signals from the receiver and passes the resulting data stream through the digital filter to remove spurious transmissions that may be caused by attenuation of the LIN bus signal. Therefore, this module improves the performance of the LIN protocol in harsh environments and minimizes problems in synchronization and data sampling.
Synchronizer The synchronizer module extracts the required information from the synchronization domain to determine the accurate sampling rate of the encoder and decoder. The module has an internal crystal oscillator and uses a technique that minimizes the rounding / rounding errors that occasionally occur in traditional UART technology. The main advantage of the synchronous machine is that it can execute the LIN protocol with a lower clock frequency. For example, a 250KHz master clock and a 15% tolerance can be used to obtain accurate communication. In addition, AMIS's program achieves a relatively large range of changes in duty. A typical UART can achieve a duty cycle change of 33% to 66% with zero error of the crystal. However, the use of AMIS solutions can achieve a duty cycle of 12 ~ 88% change, and can fully adapt to the crystal oscillator error. While providing a larger tolerance for the physical layer parameters, it also improves the electromagnetic compatibility that has a greater impact on the duty cycle.
Identifier filter and its dynamic management The master node issues different slave instruction identifiers as needed during the initial and running of the system. To this end, the slave node must contain a certain number of registers. The ROM instruction number array refers to the different instructions executed from the node, and contains the corresponding identifier in RAM or EEPROM. The address register module recognizes different slave nodes on the same LIN bus, while the second ROM array recognizes different slave nodes for different applications and execution processes. The identifier filter determines whether the instruction is executed according to the assigned identifier. If the identifier exists in the queue, the instruction is executed, otherwise it is not executed.
Error correction The error recognition module is at the data link layer, while error correction is performed at the application layer. Therefore, the amount of error is defined in the software by the embedded microcontroller. The error correction module in the application layer contains a status register, each error has a corresponding error flag, and the flag generates an interrupt request to the core of the microprocessor. The error flag can be cleared by reading the status register. Each error interrupts the communication directly, resulting in a bit error to stop sending bytes. Then this frame of information is ignored and the slave node waits for the next interruption domain.
Frame Buffer Frame buffer is another way to minimize the interrupt to the microprocessor core. It is used in conjunction with the identifier filter to reduce the number of interrupts to once per frame. The buffer contains 17 bytes (one identifier, eight transmit bytes, and eight receive bytes).
Core / state machine and application interface AMIS can provide different cores as needed. The core and the LIN controller are connected by an interrupt signal and a special function register (SFR). The LIN controller can be regarded as a peripheral device on the SFR bus. In addition to these LIN bus characteristics, as with similar semiconductor processing technology platforms, AMIS has developed an extensive IP module library, including two ⑵ and SAR ADC modules, delay triggers with output currents up to 0.3A and output currents up to 3A H bridge. Of course, using slave nodes is only a part of the whole function, and providing them with enough power to integrate them in today's automobiles is the next important challenge for automotive electrical engineers.
42V power supply technical solution In an ideal automotive power supply solution, the power level will be converted from the traditional 12V battery voltage to a 42V power system. In the 42V system, the power level will continue to increase. For example, the maximum working voltage of the entire life cycle of the system is set at 50V. If there is a maximum dynamic overvoltage of 8V, the power supply voltage will reach 58V. Adding a 12V externally driven load pump will make the system voltage demand reach 70V, and then add an ESD protection window, the system voltage will reach 80V. Moreover, semiconductor devices of automobiles not only have to withstand higher voltages, but also must have sufficient robustness to meet their harsh operating environment, for example, should meet the requirements of operating temperature in the range of -40 ℃ ~ +200 ℃. So far, withstanding higher voltages and meeting the demands of demanding operating conditions has been a major obstacle to the application of smart 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. Meet the harsh operating conditions of 42V automotive systems. Devices developed by this technology include motor control drivers, DC-DC converters, high-precision analog circuits with bandwidth filters, and ADCs and DACs. And I3T80 can be embedded and integrated more than 150,000 gates in total, and its communication protocol modules include PLL, USB, bus protocol controller, CAN and LIN communication controller. In addition, it also provides ROM and RAM memory.
Conclusion In new automotive electronics applications, as electronic components continue to increase, automotive designers are looking for a reasonable solution. In this way, a highly integrated and highly reliable SoC solution came into being. The technical requirements of this solution can simplify the execution steps and reduce the cost of control and interface with different electronic systems. AMIS 'high-voltage, mixed-signal technology meets this need. It combines a semiconductor solution with a dedicated IP module, can meet any standard interface communication bus (LIN, CAN) node applications, and is compatible with 42V voltage level schemes.
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