This application claims the priority of Chinese patent application number 201810327003.4, filed on Apr. 12, 2018, the entire contents of which are incorporated herein by reference.
The present invention relates to the field of semiconductor technology and, in particular, to a charge pump.
A charge pump usually has a number of stages which are cascaded to achieve a desired voltage and a corresponding drive ability. An existing charge pump typically includes a charge-pump cascade consisting of multiple charge-pump stages connected in series and a voltage regulator. For example, in a five-stage charge-pump cascade structure, an input of the first charge-pump stage is connected to a supply voltage, while a high voltage is supplied at an output of the fifth charge-pump stage.
The voltage regulator is configured for voltage clamping and typically includes a comparator and two resistors connected in series between the output of the fifth charge-pump stage and the ground. A feedback voltage output from the connection node between the two resistors is coupled to an inverting input of the comparator, with a non-inverting input of the comparator being coupled to a reference voltage.
Such an existing charge pump can easily satisfy a design need for an output voltage up to 7-8 V and a drive current of 10-30 μA. However, some practical applications may impose higher requirements on charge pumps. For example, for an EEPROM, a high voltage of 7 V may satisfy the need of its programming operations, but its data reading operations may require a voltage of for example 2-3 V, which is lower than the programming voltage and higher than the supply voltage. At the same time, a relatively great drive current of 200-300 μA is required. The conventional practice to address the need for such a great drive current is to increase the capacitance and the number of cascaded stages. However, this will greatly expand the size of the charge pump. Thus, the conventional charge pump is faced with the dilemma of having to increase its capacitance and stage count at the expense of compromised efficiency and size expansion in order to provide a lower voltage and a greater drive current.
It is an object of the present invention to provide a charge pump so as to overcome the problem of a lack of flexibility associated with the conventional charge-pump cascades.
To this end, the present invention provides a charge pump, comprising:
a plurality of sequentially connected charge-pump stages;
a plurality of first switches, each coupled between an output of a corresponding one of the charge-pump stages and an output of the charge pump;
a plurality of second switches, each coupled between an output of a corresponding one of the charge-pump stages and an input of an immediately succeeding one of the charge-pump stages; and
a plurality of third switches, each coupled between an output of a corresponding one of the charge-pump stages and an input of the charge pump,
wherein a charge-pump cascade structure is formed by individually configuring an open or close status of each of the first, second and third switches, and wherein a number of series-connected charge-pump stages and a number of parallel-connected charge-pump stages in the charge-pump cascade structure are determined by the open or close status of the respective first, second and third switches, and,
wherein a greater number of the series-connected charge-pump stages in the charge-pump cascade structure, enable a higher output voltage of the charge pump, and the greater a number of the parallel-connected charge-pump stages in the charge-pump cascade structure, enable a higher drive current produced by the charge pump.
Optionally, in the charge pump, in among the plurality of sequentially connected charge-pump stages, an input of a leading one of the charge-pump stages serves as an input of the charge-pump cascade structure, and an output of a trailing one of the charge-pump stages serves as an output of the charge-pump cascade structure.
Optionally, in the charge pump, an input of the charge-pump cascade structure may be coupled to a supply voltage and an output of the charge-pump cascade structure is coupled to a load.
Optionally, in the charge pump, a number of the first switches may be one less than a number of the charge-pump stages.
Optionally, in the charge pump, a number of the second switches may be one less than a number of the charge-pump stages.
Optionally, in the charge pump, a number of the third switches may be one less than a number of the charge-pump stages.
Optionally, in the charge pump, the plurality of charge-pump stages are connectable in parallel by closing each of the first and third switches and opening each of the second switches.
Optionally, in the charge pump, the plurality of charge-pump stages are connectable in series by opening each of the first and third switches and closing each of the second switches.
Optionally, in the charge pump, each of the charge-pump stage may comprise two sub-stages which are connected in series, one of the two sub-stages having an input serving as an input of the charge-pump stage, the other one of the two sub-stages having an output serving as an output of the charge-pump stage.
Optionally, the charge pump may further comprise a plurality of fourth switches, wherein in each of the charge-pump stages, a node between the two sub-stages is connected to a supply voltage via a corresponding one of the fourth switches and the sub-stages is e coupled to a clock signal.
In the charge pump proposed in the present invention, through a configuration of the first, second and third switches, and opening or closing of the first, second and third switches to change the connection relationship among the charge-pump stages (series or parallel), thereby forming different charge-pump cascade structures enabling provide different output voltages and drive current abilities that can address various drive ability needs for circuits. In this manner, a great drive current can be achieved without increasing the capacitance or the number of stages, offering significant size and cost savings.
The charge pump constructed in accordance with this invention will be described below in further detail with reference to the accompanying drawings and specific embodiments. Features and advantages of the invention will be more apparent from the following detailed description, and from the appended claims. It is noted that the figures are provided in a very simplified form not necessarily presented to scale, with the only intention to facilitate convenience and clarity in explaining the embodiments of the invention.
The core concept of the present invention is to provide a charge pump so as to overcome the problem of lacking flexibility associated with the conventional charge-pump cascades.
To this end, the charge pump of the present invention includes: a plurality of charge-pump stages connected sequentially; a plurality of first switches, each coupled between an output of a corresponding one of the charge-pump stages and an output of the charge pump; a plurality of second switches, each coupled to an output of a corresponding one of the charge-pump stages at one end and to an input of an immediately succeeding one of the charge-pump stages at the other end; and a plurality of third switches, each coupled between an output of a corresponding one of the charge-pump stages and an input of the charge pump. The first, second and third switches are individually opened or closed to form different charge-pump cascade structures with various output voltages and drive currents. The greater the number of charge-pump stages connected in series in a charge-pump cascade structure is, the higher the output voltage of the charge pump will be. In another aspect, the greater the number of charge-pump stages connected in parallel in a charge-pump cascade structure is, the higher the drive current produced by the charge pump will be.
As shown in
The charge pump may further include a voltage regulator configured for voltage clamping. The voltage regulator may include a comparator 2, a first resistor R1 and a second resistor R2. The first resistor R1 is connected to an output of the charge-pump cascade structure at one end and to the second resistor R2 at the other end. The other end of the second resistor R2 may be grounded. The comparator 2 may have: a non-inverting input coupled to a reference voltage Vref; an inverting input coupled to a feedback voltage Vfb provided at the connection node of the first resistor and the second resistor; and an output that outputs a clock signal clken.
Specifically, in the charge pump, an input of a leading one (i.e., 1a) of the plurality of sequentially connected charge-pump stages may serve as the input of the charge-pump cascade structure, and an output of a trailing one (i.e., 1d) of the plurality of charge-pump stages may serve as the output of the charge-pump cascade structure. The input of the charge-pump cascade structure may be coupled to a supply voltage VCC, with its output coupled to a load Vppi.
Preferably, the number of the first switches K1 is one less than the number of the charge-pump stages. The number of the second switches K2 is one less than the number of the charge-pump stages. And the number of the third switches K3 is one less than the number of the charge-pump stages.
Specifically, if all the switches K2 are opened and all the switches K1, K3 are closed, a parallel-connected charge-pump cascade structure is formed. As shown in
As shown in
Alternatively, as shown in
As shown in
In the charge pump proposed in the present invention, through a configuration of the plurality of first, second and third switches K1, K2, K3, and through the opening or closing of the first, second and third switches K1, K2, K3, the connection relationship among the charge-pump stages can be correspondingly changed, thereby forming different charge-pump cascade structures enabling the provision of different output voltages and different drive current abilities that are required to address various drive ability needs for circuit. In this manner, a great drive current can be achieved without increasing the capacitance or the number of stages, offering significant size and cost savings.
In summary, various configurations of the charge pump have been detailed in the above embodiments. Of course, the present invention includes, but not limited to, the configurations disclosed above, and any and all modifications made to these configurations are considered to fall within the scope of the invention. Those skilled in the art can extend the inventive ideas in many ways.
The description presented above is merely that of some preferred embodiments of the present invention and does not limit the scope thereof in any sense. Any and all changes and modifications made by those of ordinary skill in the art based on the above teachings fall within the scope as defined in the appended claims.
Number | Date | Country | Kind |
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201810327003.4 | Apr 2018 | CN | national |