Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Reexamination Certificate
2001-04-11
2004-02-17
Cunningham, Terry D. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
C327S537000, C363S059000
Reexamination Certificate
active
06693483
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a charge pump configuration for matching a charge pump to the prevailing conditions. The charge pump configuration has a charge pump which, in order to generate a charge pump current, has a plurality of interconnected pump stages with at least one respective pump capacitor.
It is a widely known fact, which requires no further explanation, that particular applications in integrated semiconductor circuits frequently require a voltage that is different than the supply voltage. So long as the magnitude of the voltage that is to be generated is smaller than the supply voltage applied to the integrated semiconductor circuit in question, this can still be achieved using relatively simple devices. The situation is different, however, if the magnitude of the voltage that is to be generated in the integrated semiconductor circuit is larger than the corresponding supply voltage. Particularly in integrated semiconductor memories, such as a flash memory, an EEPROM, a DRAM or an FRAM etc., very high positive and also negative voltages are required from time to time during operation. At the same time, however, the constant development toward smaller and smaller semiconductor configurations require a continuous reduction in supply voltage. Thus, in order to be able to produce relatively high voltages efficiently and also with the aforementioned low supply voltages, special pump technology is required.
For this, use is generally made of charge pumps having a plurality of pump stages which operate on the basis of the principle of capacitive voltage multiplication and, in the simplest case, have one MOS diode and one capacitor per pump stage.
A generic charge pump having a multiplicity of pump stages is described in Published, European Patent Application EP 0 865 149 A2 (corresponding to U.S. Pat. No. 6,046,625). A charge pump, known from EP 0 865 149 A2, has multiple pump stages for step-by-step charge transfer from a power supply on one side, which outputs the supply voltage, to a load capacitor on the other side of the charge pump, at which the increased voltage can be tapped off. Charge is transported to the load capacitor via a plurality of diodes and pump capacitors, which are a component part of the individual pump stages and together form the power path. In this context, the diodes are alternately turned on and off, and the pump capacitors are alternately charged and discharged.
For such a charge pump, the following is generally true in the steady, that is to say a settled state:
VL=n·VDD+VIN−n·IL/f·C,
where VL and IL denote an output potential and an output current, respectively, of the charge pump, n denotes the number of pump stages, VDD denotes the supply potential, VIN denotes the input potential, C=C
1
+C
2
+. . . + Cn denotes the total capacitance and f denotes the frequency of the charge pump configuration. In this case, n≦n
worst case
is a flexible variable and fundamentally determines an efficiency &eegr; of the charge pump, where &eegr;=PL/Pin corresponds to a ratio of a power output from the charge pump to the input power. In this context, n
worst case
denotes the minimum number of pump stages in the charge pump configuration which needs to be provided in order to configure the charge pump configuration for all conceivable permutations of input and output voltages/currents.
In the aforementioned charge pump, the number of pump stages and hence of pump capacitors n first needs to be configured for the worst case, that is to say for a minimal supply potential and input potential and a maximum output potential/current required. Since the worst case generally arises very rarely, the charge pump typically has too high a rating for normal operation, which results in poor efficiency. Therefore, the charge pump consumes much more power than is actually required.
Since the aforementioned charge pumps are also increasingly used in contactless electrical and electronic systems, for example mobile phones, chip cards, smart cards or wireless devices used in medicine, in which the power is generally supplied by a battery or a storage battery and is thus limited, an additional requirement here is for the total power consumption of the system to be kept as low as possible in order to permit a long operating life. Charge pump configurations based on the prior art meet this demand only to a limited extent or not at all, however.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a charge pump configuration that overcomes the above-mentioned disadvantages of the prior art devices of this general type, which can be matched to the prevailing conditions as best as possible in terms of its efficiency.
With the foregoing and other objects in view there is provided, in accordance with the invention, a charge pump configuration. The charge pump configuration includes a charge pump for generating a charge pump current and has a plurality of interconnected pump stages each with at least one pump capacitor. A device is connected to the charge pump and is used to turn off at least one of the interconnected pump stages on a basis of prevailing conditions that need to be taken into account.
Accordingly, the charge pump configuration is provided which is characterized in that a device is provided which can be used to bridge or turn off at least one of the pump stages on the basis of the conditions which need to be taken into account.
The pump stages needed by the charge pump configuration are optimally chosen for the present operating point on the basis of input and output voltages and currents, which allows the efficiency of the charge pump configuration to be set in an optimum fashion. In this case, the charge pump is shortened by an appropriate number of pump stages. The shortening of the charge pump is effected very simply by bridging or by disconnecting pump stages that are not required. In this context, the output current or output voltage of the charge pump can be measured and evaluated by a measuring device. On the basis of the output current or output voltage, a regulating signal is then produced which is fed back to the charge pump as a controlled variable. The regulating signal can be used to disconnect or bridge one or more pump stages which are typically not required.
Alternatively, it would also be conceivable to provide a desired output current or a desired output voltage from the charge pump by a suitable selection of the number of pump stages. In this way, the charge pump configuration having different output currents or output voltages can be produced in a defined manner, according to application.
In the simplest embodiment, pump stages which are not required can be disconnected or bridged by an A/D converter which uses the analog output signal from the charge pump to produce a digitized output signal which is supplied to a downstream-connected up/down counter or to a shift register. The shift register or up/down counter produces a digital regulating signal from the digitized output signal. In the simplest case, the digital regulating signal can be used as an enable signal for driving the individual pump stages, in order to turn them off.
The simplest way of shortening the charge pump configuration is from the beginning of the pump, that is to say from the input of the charge pump, but in principle the configuration can be shortened at any point of the charge pump.
The principle of shortening the charge pump is particularly advantageous with all forms of positive and also negative pumps. Charge pumps with feedback become useful only when shortened in accordance with the invention.
It is particularly advantageous, as is yet to be described in detail for the charge pump configuration below, if each of the pump stages can be disconnected or bridged individually and independently of each of the other pump stages. In practice, however, it is entirely sufficient if a few pump stages—typically one or two—are disconnected by suitable circuit
Bloch Martin
Deml Christoph
Cunningham Terry D.
Greenberg Laurence A.
Infineon - Technologies AG
Mayback Gregory L.
Stemer Werner H.
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