Bootstrapped CMOS driver

Details Bootstrapped CMOS driver Bootstrapped CMOS driver

1999-08-25

2001-06-05

Tran, Toan (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Specific identifiable device, circuit, or system

With bootstrap circuit

C327S390000

Reexamination Certificate

active

06242973

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a CMOS driver for driving a large capacitive load, and more particularly to a bootstrapped CMOS driver for a low-voltage application.
2. Description of the Background Art
In general, a CMOS VLSI circuit having a large fan-out or a long interconnect metal line or a CMOS output pad driver have a considerably large capacitive load. Accordingly, design of a driver circuit for driving a large capacitive load is very important for the driver circuit itself determines an operation speed of the system.
FIG. 1
illustrates a conventional tapered CMOS driver
1
to drive a large capacitive output load. As shown therein, the tapered CMOS driver
1
consists of a chain of inverters each of which employs a large size transistor progressing toward to a load.
However, when being scaled a supply voltage to reduce power consumption, there is a problem in that the operation speed of the tapered CMOS driver
1
is considerably reduced, because a threshold voltage of a MOS device constituting each inverter can not be reduced at the same rate as the supply voltage. Accordingly, to overcome such a problem, there has been introduced a BiCMOS driver that uses a driving capacity of a bipolar device. But, to apply the bipolar device to the CMOS process technology, a high cost premium is required.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a bootstrapped CMOS driver that improves a bootstrap efficiency.
Another object of the present invention is to provide a bootstrapped CMOS driver which is applicable at a relatively low voltage and which can be fabricated at a low cost.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a bootstrapped CMOS driver, which includes a drive unit consisting of pull-up and pull-down devices; and a bootstrap unit for boosting gate voltages of the pull-up and pull-down devices using a pull-up section and a pull-down section performing pull-up and pull-down operations, respectively, in accordance with a level of an input signal, wherein the pull-up section and the pull-down section can be embodied as a plurality of MOS devices and dual bootstrap capacitors controlled by a single input signal or as a plurality of MOS devices and a single bootstrap capacitor controlled by two input signals. Additional advantages, objects, and features of the invention will be set forth in part in the description which follows an in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.


REFERENCES:
patent: 5568081 (1996-10-01), Lui et al.
patent: 5729165 (1998-03-01), Lou et al.
patent: 5790612 (1998-08-01), Chengson et al.

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