Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Reexamination Certificate
1998-12-29
2001-02-27
Ton, My-Trang Nu (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
C327S537000
Reexamination Certificate
active
06194954
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device, and in particular, to a voltage controlled generator for a semiconductor device which makes it possible to actively control the pumping period of a bias voltage supplied to a semiconductor device using a voltage controlled oscillator.
2. Description of the Conventional Art
Recently, the semiconductor circuit is designed to have a characteristic that a substrate bias voltage is changed from a ground voltage GND to a negative bias voltage for thereby supplying a VBB voltage for the reason that the VBB voltage decreases a substrate bias effect and a junction electrostatic capacity of a threshold voltage, increases a punch through voltage and prevents a data damage due to undershoot.
The conventional substrate bias voltage (VBB) generation circuit is formed of a detector detecting a substrate bias voltage, a ring oscillator formed of an odd number of inverters and a charge pump. In the conventional circuit, when a VBB level is detected by the VBB detector, the ring oscillator is operated at a predetermined oscillation period, so that the VBB voltage generated based on the charge pump is supplied to the semiconductor substrate.
The thusly constituted VBB generation circuit should stably generate a substrate bias voltage level and a large Icp current based on a low electric power.
However, in the conventional VBB generation circuit, since a ring oscillator is operated at a constant oscillation period, if a substrate bias voltage variation occurs, the VBB voltage level of the charge pump does not quickly reach the substrate bias voltage, so that the efficiency of the charge pump is decreased, and the power consumption is increased.
In addition, the conventional step-up voltage generation circuit has a characteristic that a high voltage pulse higher than an external power voltage Vcc is applied to a semiconductor device for thereby compensating the threshold voltage loss of the transistor. The above-described conventional step-up voltage generation circuit is formed of a detector detecting the level of a step-up voltage VPP, a ring oscillator, and a charge pump. The step-up voltage generation circuit detects the VPP voltage level by the detector like the substrate bias voltage generation circuit and opens/closes the ring oscillator for thereby determining the operation of the charge pump.
Therefore, when the step-up voltage generation circuit is formed of a ring oscillator as a frequency oscillation device, since the signal period of the oscillator is constant, it is impossible to implement a fast pump speed of the charge pump when the level of the step-up voltage is decreased below a reference level for thereby decreasing the efficiency of the charge pump and increasing the power consumption.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a voltage controlled generator for a semiconductor device which overcomes the aforementioned problems encountered in the conventional art.
It is another object of the present invention to provide a voltage controlled generator for a semiconductor device which is capable of supplying a stable substrate bias voltage by extending the period of a voltage controlled oscillator when a substrate bias voltage level exceeds a predetermined level VPP by which it is possible to overcome the problem that an oscillation period of a VBB voltage generation circuit is not quickly controlled for a predetermined time against the level variation of a substrate bias voltage for thereby rapidly pumping a charge pump and is capable of decreasing or stopping a pumping operation by decreasing the period of a voltage controlled oscillator when the substrate bias voltage level drops below a VPP level.
It is another object of the present invention to provide a voltage controlled generator for a semiconductor device which is capable of supplying a stable step-up voltage by extending or shortening the oscillating period of a voltage controlled oscillator when a substrate bias voltage level exceeds or drops below a predetermined level VBB by which it is possible to overcome the problem that an oscillation period of a VBB voltage generation circuit is not quickly controlled for a predetermined time against the level variation of a step-up voltage.
In order to achieve the above objects, there is provided a voltage controlled generator for a semiconductor device according to a first embodiment of the present invention which includes a control level generator generating at least one control signal for detecting a substrate bias voltage level from a substrate of a semiconductor device and adjusting the width of an oscillation period to a set level in accordance with the detected signal, a voltage control oscillator generating a signal in which the width of an oscillation period is varied to the set level in response to an output signal from the control level generator, and a charge pump supplying a stable bias voltage to the substrate of the semiconductor device by increasing or decreasing a pumping speed in response to an output signal from the voltage control oscillator.
In order to achieve the above objects, there is provided a voltage controlled generator for a semiconductor device according to a second embodiment of the present invention which includes a control level generator generating at least one control signal for detecting a voltage level from a semiconductor device using a step-up voltage and adjusting the width of an oscillation period to a set level in accordance with the detected signal, a voltage control oscillator generating a signal in which the width of an oscillation period is varied to the set level in response to an output signal from the control level generator, and a charge pump supplying a stable step-up voltage to the semiconductor device by increasing or decreasing a pumping speed in response to an output signal from the voltage control oscillator.
Preferably, a control level generator includes a pull down control level generator generating a pull down voltage which is in inverse proportional to the voltage detected in a substrate of a semiconductor device.
More preferably, the control level generator includes a pull up control level generator generating a pull up voltage which is in inverse proportion to the voltage level detected in a substrate of the semiconductor device.
In the substrate bias circuit according to the present invention, it is possible to decrease a power consumption by controlling the period of a VBB pumping and to decrease a layout area by simplifying the circuit.
Preferably, a control level generator includes a pull up control level generator generating a pull up voltage which is in proportion to the voltage level detected in a semiconductor device requiring a step-up voltage or a pull down control level generator generating a pull down voltage which is in inverse proportion to the voltage level detected in a semiconductor device requiring a step-up voltage.
Therefore, in the step-up voltage generation circuit according to the present invention, it is possible to decrease the power consumption by actively controlling the pumping period of a charge pump in accordance with a VPP level variation and to decrease the layout area by simplifying the circuit.
Additional advantages, objects and other features of the invention will be set forth in part in the description which follows and 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 as a result of the experiment compared to the conventional arts.
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patent: 5043677 (1991-08-01), Tomassetti et al.
patent: 5262989 (1993-11-01), Lee et al.
patent: 5304859 (1994-04-01), Arimoto
patent: 5315557 (1994-05-01), Kim et al.
patent: 5440277 (1995-08-01), Ewen et al.
patent: 5561385 (1996-10-01), Choi
patent: 5602
Chun Ki-Chang
Kim Saeng-Hwan
Lee Kwang-Jin
Hyundai Electronics Industries Co,. Ltd.
Nu Ton My-Trang
Oliff & Berridg,e PLC
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