Output driver device with electrostatic discharge protection

Details Output driver device with electrostatic discharge protection Output driver device with electrostatic discharge protection

1999-06-21

2001-01-16

Jackson, Stephen W. (Department: 2836)

Electricity: electrical systems and devices

Safety and protection of systems and devices

Transient responsive

C361S056000, C361S091100, C361S127000, C361S118000

Reexamination Certificate

active

06175482

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
The present invention relates in general to semiconductor devices and more particularly to an output driver device with electrostatic discharge protection.
BACKGROUND OF THE INVENTION
Conventional open drain differential output drivers are protected from failure due to electrostatic discharge by connecting the output node to a separate electrostatic discharge transistor. The electrostatic discharge transistor provides a path to ground from the output pad for an electrostatic discharge strike in order to avoid damage to the output driver. However, the output transistor providing the actual output must not only drive its drain load but also the load of the electrostatic discharge transistor. The additional load driven by the output transistor is detrimental to performance of the output driver, especially for a high speed input/output device operating at gigahertz speeds. Therefore, it is desirable to reduce the load driven by an output driver and enhance high speed performance while still providing electrostatic discharge protection.
SUMMARY OF THE INVENTION
From the foregoing, it may be appreciated that a need has arisen for an output driver device with a reduced load for enhanced high speed performance and with electrostatic discharge protection. In accordance with the present invention, an output driver device with electrostatic discharge protection is provided that substantially eliminates or reduces disadvantages and problems associated with conventional output driver devices with electrostatic discharge protection.
According to an embodiment of the present invention, there is provided an output driver device with electrostatic discharge protection that includes a first diffusion node formed into a substrate layer. The first diffusion node is coupled to a ground potential. A second diffusion node is formed in the substrate layer such that the first and second diffusion nodes form a bias transistor. A third diffusion node is formed in the substrate layer such that the second and third diffusion nodes form an output transistor. The third diffusion node is coupled to an output pad. The first, second, and third diffusion nodes form a non-metal path from the output pad to the ground potential to absorb an electrostatic discharge strike occurring on the output pad, protecting the output driver from damage.
The present invention provides various technical advantages over conventional output drivers with electrostatic discharge protection. For example, one technical advantage is in reducing the load driven by the output transistors in the output driver device. Another technical advantage is in reducing drain capacitance and layout area for the output driver device. Yet another technical advantage is in having the output driver also absorb any electrostatic discharge strike. Other technical advantages may be readily ascertained by those skilled in the art from the following figures, description, and claims.


REFERENCES:
patent: 4734752 (1988-03-01), Liu et al.
patent: 4855620 (1989-08-01), Duvvury et al.
patent: 5028819 (1991-07-01), Wei et al.

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