Features of the new physical layer interface device MC33661 and its application in automotive electronics

This article introduces the new physical layer interface device MC33661 designed specifically for LIN bus applications in the automotive industry and briefly describes its application in automotive electronics.

LIN bus

With the rapid development of information technology, the proportion of automotive electronic products in automobiles is increasing, and automotive electronic technology has gradually become one of the characteristics of automotive high-tech. LIN (Local Interconnect Network) is a low-cost serial communication network, which is now more used to realize the control of distributed electronic systems in automobiles. The goal of LIN is to provide auxiliary functions for existing automotive networks (such as CAN bus). The LIN bus is based on the universal asynchronous serial port ( UART ) of computers , which is originally point-to-point, and is equipped with a bus driver suitable for multi-point communication, plus the LIN bus communication protocol, to form a cheap serial bus control system. The LIN bus is an auxiliary bus for high-end communication buses, such as the CAN (Controller Area Network) bus. In situations where the bandwidth and functions of the CAN bus are not required, such as the control of doors, windows, rearview mirrors, and the communication between intelligent sensors and brake devices, the use of the LIN bus can greatly save costs. LIN bus driver MC33661.

In the past, LIN bus drivers included MC33399, etc. As time went by, their shortcomings gradually emerged, such as the single mode, the inability to effectively adjust the flip frequency, which sometimes caused the device to consume a lot of power, and sometimes the driving power was insufficient, etc. The birth of MC33661 has greatly improved this situation.

The MC33661 chip uses an ordinary 8-pin plastic package.

Operation Mode and Application Circuit

The multiple operation modes of MC33661 greatly improve the performance of LIN bus driver. MC33661 has a series of operation modes such as normal mode, low speed mode, high speed mode, sleep mode, etc. This greatly enriches the functions of the chip. Users can set the chip mode according to different needs, which improves the efficiency of the chip while minimizing the loss. This gives it a great advantage in the competition with the same type of chips and is a strong support for LIN bus applications.

When the MC33661 is in normal mode, the LIN bus is in normal working state, the operating frequency and timing of the device conform to the LIN bus protocol specification, and the communication rate is 20kbps.

When the LIN bus is used in ECU testing and downloading programs to the microcontroller , the MC33661 can use the high-speed mode and the communication frequency can reach 100kbps.

MC33661 can enter low speed mode to further reduce the electromagnetic radiation level of the LIN bus, although the electromagnetic radiation level in normal working mode is not high.

MC33661 has a sleep mode. In sleep mode, the power consumption is extremely low. The information required for quick startup is retained during sleep mode, so quick startup can be achieved.

Typical circuit using MC33661 as master node. When used as slave node driver, it is not necessary to connect the diode and pull-up resistor of Mask node pull up end , and directly connect to LIN bus driver end LIN bus. On the microcontroller end, directly use the send and receive ends of SCI port to control communication, and use an I/O port of microcontroller as output to control working mode. The power supply end is directly connected to 12V car battery. The driver enters sleep mode when the whole vehicle is powered off.