Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Reexamination Certificate
1997-07-28
2001-02-06
Kim, Jung Ho (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
C363S060000, C363S063000
Reexamination Certificate
active
06184741
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a bidirectional charge pump, and more particularly to a bidirectional charge pump used in CMOS memory devices such as EPROMs, EEPROMs and Flash EPROMs.
2. Discussion of the Related Art
In several integrated circuits it is necessary to generate, internally to the chip, voltages which are higher than or opposite in sign of the supply voltage of the chip. This can be done by means of charge pumps. For example, in a single-power-supply Flash EPROM, it is necessary to generate a positive voltage higher than the supply voltage (VDD) for programming memory cells of the EPROM, and a negative voltage for erasing the memory cells.
Up to now, distinct charge pumps have been used to generate different voltages: positive charge pumps for generating voltages higher than the supply voltage, and negative charge pumps for generating negative voltages.
On the other hand, it is known that the main problem of the integration of a charge pump is the large chip area occupied by the capacitors of the charge pump. The necessity of providing more than one charge pump exacerbates this problem.
SUMMARY OF THE INVENTION
In view of the state of the art described, it is an object of the present invention to provide a bidirectional charge pump, i.e. a charge pump that can be used to generate both positive voltages higher than the supply voltage, and negative voltages.
In one embodiment of the present invention a charge pump is provided. The charge pump includes at least one charge pump stage including a first diode, and a capacitor, an anode of the diode forming a first terminal of the charge pump, a second diode having an anode connected to the cathode of the first diode and a cathode forming a second terminal of the charge pump, first switching means for selectively coupling the first terminal of the charge pump to a supply voltage, and a second switching means for selectively coupling the second terminal of the charge pump to a reference voltage, the first switching means and the second switching means being respectively closed and opened in a first operating condition whereby the second terminal of the charge pump acquires a voltage of the same polarity but higher in absolute value than the supply voltage, the first switching means and the second switching means being respectively opened and closed in a second operating condition whereby the first terminal of the charge pump acquires a voltage of opposite polarity with respect to the supply voltage.
In another embodiment, a charge pump is provided for coupling to first and second terminals of a voltage supply to receive a supply voltage having a magnitude and a polarity with respect to a reference voltage and for generating a boosted voltage having a magnitude and a polarity. The charge pump includes a first input coupled to the first terminal of the voltage supply to receive the supply voltage, a second input coupled to the second terminal of the voltage supply to receive the reference voltage, a charge pump circuit having a first voltage node and a second voltage node, the charge pump circuit being configured to transfer electrical charge from the first node to the second node. The charge pump further comprises a first switch that selectively couples the first node of the charge pump circuit to the first input, and a second switch that selectively couples the second node of the charge pump circuit to the second input.
In another embodiment, a charge pump is provided for coupling to a voltage supply to receive a supply voltage having a magnitude and a polarity with respect to a reference voltage for generating a boosted voltage having a magnitude and a polarity. The charge pump includes a charge pump circuit having a first voltage node and a second voltage node, the charge pump circuit being configured to transfer electrical charge from the first node to the second node, means for coupling the charge pump circuit to the first input for a first mode of operation of the charge pump for producing a voltage at the first node having a polarity opposite the polarity of the supply voltage and having a magnitude greater than the magnitude of the supply voltage, and means for coupling the charge pump circuit to the voltage supply for a second mode of operation of the charge pump circuit for producing a voltage at the second node having a polarity equal to the polarity of the supply voltage and having a magnitude greater than the magnitude of the supply voltage.
In another embodiment of the present invention, a method is provided for generating a boosted voltage having a magnitude and a polarity with respect to a reference voltage using a supply voltage having a magnitude and a polarity with respect to the reference voltage. The method includes steps of providing a charge pump circuit having a first voltage node and a second voltage node, the charge pump circuit being configured to transfer electrical charge from the first node to he second node, applying the supply voltage to the first node of the charge pump circuit to produce a boosted voltage at the second node, the boosted voltage having a polarity equal to the polarity of the supply voltage and having a magnitude greater than the magnitude of the supply voltage, and applying the reference voltage to the second node of the charge pump circuit to produce a boosted voltage at the first node, the boosted voltage having a polarity opposite the polarity of the supply voltage and having a magnitude greater than the magnitude of the supply voltage.
In another embodiment of the present invention a memory device is provided. The memory device includes a first input to receive a supply voltage having a magnitude and a polarity with respect to a reference voltage, a second input to receive the reference voltage, a charge pump coupled to the first and second inputs to respectively receive the supply voltage and the reference voltage, the charge pump including a charge pump circuit having a first voltage node and a second voltage node, the charge pump circuit being configured to transfer electrical charge from the first node to the second node, a first switch that selectively couples the first node of the charge pump circuit to the first input of the memory device, and a second switch that selectively couples the second node of the charge pump circuit to the second input of the memory device, and a first clock input to receive a first clock signal. The memory device further includes a clock generator coupled to the first clock input of the charge pump circuit to provide the first clock signal.
Thanks to embodiments of the present invention, it is possible to use a single charge pump for generating both positive voltages higher than the voltage supply, and negative voltages. This allows for a great reduction in the chip area of memory devices using charge pumps.
REFERENCES:
patent: 4837466 (1989-06-01), Kanauchi
patent: 4935644 (1990-06-01), Tsujimoto
patent: 4999761 (1991-03-01), Bingham et al.
patent: 5043858 (1991-08-01), Watanabe
patent: 5436587 (1995-07-01), Cernea
patent: 5606491 (1997-02-01), Ellis
patent: 5610549 (1997-03-01), Choi
patent: 5812018 (1998-09-01), Sudo et al.
Campardo Giovanni
Ghilardelli Andrea
Mulatti Jacopo
Galanthay Theodore E.
Kim Jung Ho
Morris James H.
SGS--Thomson Microelectronics S.r.l.
Wolf Greenfield & Sacks P.C.
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