Development of Multiplexing Communication ICs for Electronic Control of a Vehicle 922126

With an ever growing demand for the enhanced control of a vehicle and for the reduction of power and signal distributing wires in a vehicle, there is a pressing need for the development of Local Area Network (LAN) in a vehicle. LAN enables the exchange of various data among several electronic control units (ECUs), and results in the higher controlled performances of a vehicle and the reduction of the wires. In response to this need, two integrated circuits for vehicle multiplexing communication are developed. One is a communication control IC and the other is a bus driver/receiver IC, both based upon the standard of a PWM type of the J1850 for a communication protocol.

The communication control IC is designed to have distinctive features such as a highly fail-safe operation and the reduction of the overhead for communication imposed on a central processing unit (CPU) of the ECU. It is fabricated by CMOS technology and has a chip of 5.5mm x 5.5mm in size that contains about 14,000 transistors.

The IC for a bus driver/receiver has two distinctive features. One is a capability in the period of data transmission to exactly match the amount of current flowing into one line of a twisted pair of the bus with that of current returning from the other line of the pair. This technique of the exact matching of outgoing and returning currents will work toward preventing the generation of electromagnetic disturbances, which is quite favorable for radio reception in a vehicle. The other is a capability in the period of data reception to change a threshold voltage level for data reception when there is a fault in either one of the lines of the twisted pair of the bus. It is fabricated by bipolar technology, and has about 700 device elements in a chip of 3.0mm x 5.7mm.

This paper gives a detailed description of the features of the ICs together with the experimental results of the performances of the ICs.