Improving Automotive Design Performance with MCUs

introduction

In today's car design, people are paying more and more attention to the two aspects of intelligence and environmental protection. Because intelligent cars can bring people a high degree of safety and comfort, and in terms of environmental protection, energy saving and carbon saving can be achieved by using digital technology. Therefore, the degree of digitization in the automotive field is becoming deeper and deeper. From the power transmission system to the in-vehicle entertainment system, electronic components can be seen everywhere, and they are widely used in sensing and control.

In various systems of automotive electronics, microcontrollers (MCUs) are often used as the core of operation and control. The heavy reliance of automobiles on electronic systems has also stimulated the rapid growth of the automotive microcontroller market. Automotive microcontrollers cover low-, medium-, and high-end product levels such as 8-bit, 16-bit, and 32-bit, and each has its own suitable application system, which is roughly as follows:

8-bit MCU: Mainly used in various subsystems of the vehicle body, including fan control, air conditioning control, wipers, sunroof, window lifts, low-level instrument panels, junction boxes, seat control, door control modules and other lower-level control functions.

16-bit MCU: Mainly used in powertrain systems, such as engine control, gear and clutch control, and electronic turbine systems; also suitable for chassis mechanisms, such as suspension systems, electronic power steering, torque distribution control, and electronic pumps, electronic brakes, etc.

32-bit MCU: Main applications include instrument panel control, body control, multimedia information system (Telematics), engine control, and emerging intelligent and real-time safety systems and power systems, such as pre-crash, adaptive cruise control (ACC), driver assistance system, electronic stability program and other safety functions, as well as complex X-by-wire and other transmission functions.

1 Common interfaces of automotive MCU

CAN and LIN are relatively common interfaces.

As today's automobiles have higher and higher requirements for application functions, the systems that need to be integrated are becoming more and more complex, which has led to an increasing demand for high-end 32-bit MCUs in automotive electronic systems. Such automotive MCUs are often placed in operating environments with high heat, dust, severe vibration, and severe electronic interference, so the tolerance requirements are much higher than those of general-purpose MCUs. In addition, in the automotive application environment, automotive MCUs must be connected to multiple automotive electronic control units (ECUs), among which the most common transmission interfaces are CAN and LIN.

CAN is divided into high-speed CAN and low-speed CAN. The transmission rate of high-speed CAN can reach 1 Mbps, which is suitable for applications that emphasize real-time response, such as ABS and EMS; low-speed CAN can reach 125 Kbps, which is suitable for the control of lower-speed vehicle body parts. In addition, the types of CAN controllers can be divided into the old 1.x, the standard 2.0A and the extended 2.0B. The newer the specification, the better the performance. Among them, 2.0B can be divided into passive type and active type.

LIN is a communication solution with lower speed and lower cost than CAN. It adopts the concept of one master node and multiple slave nodes (supporting up to 16 nodes), with a data transmission rate of up to 20 kbps and a bus cable length that can be extended to up to 40 meters. It is very suitable as a distributed communication solution for simpler systems such as climate control, mirrors, door modules, seats, smart switches, and low-cost sensors.

The following will introduce the new generation of MCU technology for instrument panel control and body control, and use Fujitsu's new generation MB91770 series and MB91725 series new microcontrollers as design references. Please refer to (Figure 1).

Figure 1 Application of instrument panel control and body control MCU in automobiles (taking MB91770 series and MB91725 series as examples)