Transmitter end stage

Details Transmitter end stage Transmitter end stage

1992-02-22

1995-09-05

Westin, Edward P.

Electronic digital logic circuitry

Reliability

Parasitic prevention in integrated circuit structure

326 86, 375257, H03K 190185

Patent

active

054481805

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a transmitter end stage for a data transmission system comprising at least one control unit and data transmission lines and in particular, for a CAN (Controller Area Network) bus system having at least one CAN controller and one CAN bus.
Transmitter end stages for data transmission systems, especially for controller-area-network bus systems (CAN bus systems) are known. Digital signals from a control unit of the data bus system, for example of a CAN controller, are output to the data bus with the aid of such transmitter end stages. The transmitter end stage must not be disturbed or even damaged by feedback from the data bus. For example, a short circuit of one or more of the data lines to ground or to the power supply can occur. In addition, electromagnetic noise signals can affect the data lines and hence the transmitter end stage. One disadvantage of known transmitter end stages is that they require relatively large amounts of space. As a result, applications for such transmitter end stages are limited. For example, when such transmitter end stages are used in the CAN bus systems of a motor vehicle, it is very important that the circuit be designed to be as small as possible. Moreover, when the known transmitter end stages are installed errors can occur that could adversely affect subsequent function of the entire system. In addition, the failure probability of the transmitter end stage is relatively high in view of the large number of individual components.
Therefore, a transmitter end stage which occupies a relatively small volume yet which has a relatively low rate of failure, enhanced interference protection and minimized feedback is needed.


SUMMARY OF THE INVENTION

The transmitter end stage according to the present invention advantageously occupies a very small space and is simple to install. Manufacturing of both the transmitter end stage and the entire system into which the transmitter end stage is integrated. As a result, manufacturing costs are sharply reduced. Moreover, the failure rates of the system can be reduced with the present transmitter end stage. The present transmitter end stage does so by mounting all the circuit elements of the transmitter end stage on a semiconductor substrate so that the entire circuit is monolithically integrated.
In a preferred embodiment of the transmitter end stage, each of the data lines of the bus system is assigned to a switching stage thereby optimizing protection from interference.
In a further preferred embodiment of the transmitter end stage, the components of the end stage circuit are preferably arranged in a series circuit thereby minimizing the feedback of the components to one another. During the diffusion of layers at various areas on the substrate to manufacture the individual components, parasitic components occur which adversely affect the function of the individual circuit elements. Such feedback and parasitic components are avoided or minimized in the present invention by the layout and the chosen circuit arrangement.
In a preferred embodiment of the transmitter end, separate pre-driver stages are assigned to the electronic switches of the end stage circuits thereby significantly reducing the signal delay of the circuit. As a result, digital signals can be transmitted at a high transmission rate.
In yet another embodiment of the transmitter end stage, resistors are provided directly to the terminals of the data lines. In this manner, the interaction of the data bus with the transmitter can be influenced by appropriately choosing the resistance values of the resistors.
In another preferred embodiment, the resistances are produced by a diffusion method and are formed lying in so-called "floating tubs." As a result of the design of the topography of the resistances, in the event of electromagnetic disturbances, or short circuits of the connecting terminals CAN.sub.H or CAN.sub.L to ground or the supply voltage, the current can be limited, thereby protecting the transmitter end stage

REFERENCES:
patent: 4577211 (1986-03-01), Bynum et al.
patent: 4620310 (1986-10-01), Lvovsky et al.
patent: 4801824 (1989-01-01), Fellinger et al.
patent: 4945258 (1990-07-01), Picard et al.
patent: 5208492 (1993-05-01), Masumoto et al.

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