Internal voltage supply circuit of a semiconductor memory device with a refresh mode

An internal voltage supply circuit may Include a first internal voltage generator for receiving an external voltage and generating a first internal voltage, a second internal voltage generator for generating a second internal voltage lower than the first internal voltage, and a switching circuit responsive to a control signal, for supplying the second internal voltage to a refresh-associated circuit in a refresh mode and the first internal voltage to the refresh-associated circuit in normal mode. The control signal is enabled in the refresh mode.

FIELD OF THE INVENTION

The present invention relates to an internal voltage supply circuit, and more particularly to an internal voltage supply circuit for supplying an internal voltage lower than the voltage in normal mode to circuits of a semiconductor device, particularly circuits associated with a refresh operation, when the semiconductor device is in refresh mode, thus making it possible to reduce current consumption of the semiconductor device.

DESCRIPTION OF THE RELATED ART

Generally, in a semiconductor device, particularly a dynamic random access memory (DRAM), one memory cell is composed of one selection transistor and one data storage capacitor. In this regard, the DRAM is widely used as a semiconductor memory device suitable for increasing the integration density of a semiconductor substrate. However, because the DRAM suffers charge leakage through the storage capacitor and selection capacitor, it has to periodically perform a refresh operation of recharging DRAM cells with charges.

Recently, as semiconductor memory devices have been developed to operate at higher speeds and lower power, a lower external voltage is applied to the memory device, resulting in a reduction in the level of an internal voltage for an internal operation of the memory device. Particularly, current consumption in the refresh operation has become a very important issue associated with the low-power operation and low current consumption of the semiconductor device. However, a conventional internal voltage supply circuit has the disadvantage of, in a refresh mode, supplying a voltage of the same level as that of a voltage in a normal mode, thereby increasing the current consumption in the refresh operation. This problem with the conventional internal voltage supply circuit will hereinafter be described with reference to the annexed drawings. Here, the normal mode refers to an operation mode in which active operations except the refresh operation, namely, actual operations including a data input operation, a data output operation, etc., are performed.

FIG. 1shows the configuration of a conventional internal voltage supply circuit, andFIG. 2shows the configuration of another conventional internal voltage supply circuit. As shown in these drawings, conventionally, an external voltage VDD or internal voltage VINT is applied simultaneously to a refresh-associated circuit110and a peripheral circuit120irrespective of the operation mode of a semiconductor device. Here, the external voltage VDD and the internal voltage VINT are voltages of relatively high levels that are applied for smooth operation executions of the refresh-associated circuit110and peripheral circuit120when the semiconductor device is in a normal mode, not a refresh mode. The refresh-associated circuit110signifies a circuitry including circuit elements that are actually operated to perform a refresh operation, and the peripheral circuit120signifies a circuitry including circuit elements that are operated to perform general logic operations except the refresh operation, such as a data input operation and a data output operation.

As shown inFIG. 1or2, conventionally, the external voltage VDD or internal voltage VINT of the high level is always applied simultaneously to the refresh-associated circuit110and the peripheral circuit120. For this reason, the external voltage VDD or internal voltage VINT of the high level is applied to the refresh-associated circuit110in the refresh mode, as well as in the normal mode. In general terms, because the amount of charge to be driven in the refresh mode is determined depending on the capacitance and voltage level, the amount of current to be consumed in the refresh mode is greatly influenced by the voltage to be supplied. In conclusion, a conventional internal voltage supply circuit designed to supply the high voltage as stated above in the refresh mode, and a semiconductor device using the same are disadvantageous in that current consumption of the semiconductor device is increased, causing a reduction in power efficiency thereof.

SUMMARY OF THE INVENTION

An internal voltage supply circuit supplies an internal voltage lower than a voltage in a normal mode to circuits of a semiconductor device, particularly circuits associated with a refresh operation, when the semiconductor device is in a refresh mode, thus making it possible to reduce current consumption of the semiconductor device.

The internal voltage supply circuit may include a first internal voltage generator for generating an internal voltage lower than an external voltage. A switching circuit responsive to a control signal supplies the internal voltage to a refresh-associated circuit in a refresh mode and the external voltage to the refresh-associated circuit in a normal mode. The control signal may be enabled in the refresh mode.

The switching circuit may include a first switch for supplying the external voltage to the refresh-associated circuit in the normal mode in response to the control signal, and a second switch for supplying the internal voltage to the refresh-associated circuit in the refresh mode in response to the control signal.

The first switch may include a first PMOS transistor. The second switch may include an inverter for inversion-buffering the control signal, and a second PMOS transistor operated in response to an output signal from the inverter.

Alternatively, the first switch may include a first NMOS transistor, and the second switch may include an inverter for inversion-buffering the control signal, and a second NMOS transistor operated in response to an output signal from the inverter.

Alternatively, the first switch may include a PMOS transistor, and the second switch may include an NMOS transistor.

Alternatively, the first switch may include an NMOS transistor, and the second switch may include a PMOS transistor.

The first internal voltage generator may generate the internal voltage for a cell operation of a semiconductor device, and the external voltage may be applied simultaneously to the refresh-associated circuit and a peripheral circuit in the normal mode.

The internal voltage supply circuit may further include a second internal voltage generator that supplies an internal voltage of the same level as that of the internal voltage from the first internal voltage generator to the refresh-associated circuit irrespective of an operation mode of a semiconductor device.

An internal voltage supply circuit may include a first internal voltage generator for receiving an external voltage and generating a first internal voltage. A second internal voltage generator may generate a second internal voltage lower than the first internal voltage. A switching circuit is responsive to a control signal to supply the second internal voltage to a refresh-associated circuit in a refresh mode and the first internal voltage to the refresh-associated circuit in a normal mode. The control signal may be enabled in refresh mode.

The switching circuit may include a first switch for supplying the first internal voltage to the refresh-associated circuit in the normal mode in response to the control signal, and a second switch for supplying the second internal voltage to the refresh-associated circuit in the refresh mode in response to the control signal.

The first switch may include a first PMOS transistor, and the second switch may include an inverter for inversion-buffering the control signal, and a second PMOS transistor operated in response to an output signal from the inverter.

Alternatively, the first switch may include a first NMOS transistor, and the second switch may include an inverter for inversion-buffering the control signal, and a second NMOS transistor operated in response to an output signal from the inverter.

Alternatively, the first switch may include a PMOS transistor, and the second switch may include an NMOS transistor.

Alternatively, the first switch may include an NMOS transistor, and the second switch may include a PMOS transistor.

The second internal voltage generator may generate the second internal voltage for a cell operation of a semiconductor device, and the first internal voltage may be applied simultaneously to the refresh-associated circuit and a peripheral circuit in the normal mode.

The internal voltage supply circuit may further include a third internal voltage generator for supplying a third internal voltage of the same level as that of the second internal voltage from the second internal voltage generator to the refresh-associated circuit irrespective of an operation mode of a semiconductor device.

DETAILED DESCRIPTION

FIGS. 3 and 5show the configuration of an internal voltage supply circuit according to a first described embodiment. As shown inFIGS. 3 and 5, an internal voltage supply circuit may include an internal voltage generator230for generating an internal voltage VINT lower than an external voltage VDD, and a switching circuit240operated in response to a control signal refresh which is enabled in a refresh mode. The switching circuit240may act to supply the internal voltage VINT to a refresh-associated circuit210in the refresh mode and the external voltage VDD to the refresh-associated circuit210in a normal mode.

The switching circuit240may include, as shown inFIG. 5, a first switch for supplying the external voltage VDD to the refresh-associated circuit210in the normal mode in response to the control signal refresh, and a second switch for supplying the internal voltage VINT to the refresh-associated circuit210in the refresh mode in response to the control signal refresh. The first switch may include a PMOS transistor P21, and the second switch may include an inverter IV20and a PMOS transistor P22.

The operation of the internal voltage supply circuit with the above-stated configuration according to the first embodiment will hereinafter be described with reference toFIGS. 3 and 5in conjunction with respective operation modes of a semiconductor device.

A description will first be given of the operation of the internal voltage supply circuit in the case where the operation mode of the semiconductor device is the normal mode, namely, an operation mode in which active operations except a refresh operation (i.e., actual operations including a data input operation, a data output operation, etc.) are performed.

In the normal mode, the external voltage VDD is supplied simultaneously to the refresh-associated circuit210and a peripheral circuit220, as shown inFIG. 3. At this time, the switching circuit240acts to switch the external voltage VDD to the refresh-associated circuit210in response to the control signal refresh such that the external voltage VDD is applied to the refresh-associated circuit210in the normal mode. That is, in the normal mode, the control signal refresh assumes a low level. As a result, in the switching circuit240, as shown inFIG. 5, the PMOS transistor P21is turned on in response to the control signal refresh and the PMOS transistor P22is turned off in response to the control signal refresh, thereby causing the external voltage VDD to be applied to the refresh-associated circuit210. Consequently, in the normal mode, the external voltage VDD is applied to the refresh-associated circuit210such that operations associated with the normal mode are performed.

Here, the control signal refresh indicates that the semiconductor device is in a refresh operation. Namely, the control signal refresh remains disabled to be low in level in normal mode, and is then enabled to be high in level when the semiconductor device enters the refresh mode. The refresh-associated circuit210signifies a circuitry including circuit elements that are actually operated to perform the refresh operation, and the peripheral circuit220signifies a circuitry including circuit elements that are operated to perform general logic operations except the refresh operation, such as a data input operation and a data output operation.

Next, at the time that the semiconductor device enters the refresh mode, the internal voltage VINT, not the external voltage VDD, is supplied to the refresh-associated circuit210, as shown inFIGS. 3 and 5. That is, because the control signal refresh makes a low to high level transition in the refresh mode, the output of the inverter IV20becomes low in level to turn on the PMOS transistor P22, whereas the PMOS transistor P21is turned off, as shown inFIG. 5. As a result, the internal voltage VINT is applied to the refresh-associated circuit210. Here, the internal voltage generator230is a circuitry for generating the internal voltage VINT for a cell operation such as reading or writing of data from or into a cell. The internal voltage VINT is lower than the external voltage VDD. In other words, in the refresh mode, the internal voltage VINT lower than the external voltage VDD is applied to the refresh-associated circuit210such that operations associated with the refresh mode are performed.

As described above, according to the first embodiment, in the case where the operation mode of the semiconductor device is the refresh mode, an internal voltage lower than a voltage in the normal mode is supplied, so that current consumption of the semiconductor device can be reduced. Moreover, the internal voltage supply circuit according to the first embodiment can realize such a current consumption reduction without employing supplementary circuits for control of the supply voltage and without increasing a layout area and standby current. Therefore, an internal voltage supply circuit as described in connection with the first embodiment may provide an economic advantage in terms of the layout and power efficiency of the semiconductor device.

On the other hand, as shown inFIG. 10, the internal voltage supply circuit according to the first embodiment may further comprise a second internal voltage generator250for supplying an internal voltage of the same level as that of the internal voltage VINT from the first internal voltage generator230to the refresh-associated circuit210. The second internal voltage generator250is a circuitry for generating and supplying the internal voltage of the same level as that of the internal voltage VINT to the refresh-associated circuit210irrespective of the operation mode of the semiconductor device. This second internal voltage generator250acts to prevent noise or bouncing which may occur when the operation mode of the semiconductor device is changed between the normal mode and the refresh mode, and to fill the current when it is insufficient.

As shown inFIG. 7, the first switch of the switching circuit240may include an NMOS transistor N41, and the second switch thereof may include an inverter IV40and an NMOS transistor N42. In this case, the control signal refresh assumes a high level in the normal mode, and a low level in the refresh mode.

Alternatively, as shown inFIG. 8, the first switch of the switching circuit240may include a PMOS transistor P51, and the second switch thereof may include an NMOS transistor N51. In this case, the control signal refresh assumes a low level in the normal mode, and a high level in the refresh mode.

As another alternative, as shown inFIG. 9, the first switch of the switching circuit240may include an NMOS transistor N61, and the second switch thereof may include a PMOS transistor P61. In this case, the control signal refresh assumes a high level in the normal mode, and a low level in refresh mode.

Next, a description will be given of the internal voltage supply circuit according to a second described embodiment with reference toFIGS. 4 and 6. As shown inFIGS. 4 and 6, an internal voltage supply circuit may include a first internal voltage generator330for receiving an external voltage VDD and generating a first internal voltage VINT1, a second internal voltage generator340for generating a second internal voltage VINT2lower than the first internal voltage VINT1, and a switching circuit350operated in response to a control signal refresh which is enabled in a refresh mode. The switching circuit350acts to supply the second internal voltage VINT2to a refresh-associated circuit310in the refresh mode and the first internal voltage VINT1to the refresh-associated circuit310in a normal mode.

The switching circuit350may include, as shown inFIG. 6, a first switch for supplying the first internal voltage VINT1to the refresh-associated circuit310in the normal mode in response to the control signal refresh, and a second switch for supplying the second internal voltage VINT2to the refresh-associated circuit310in the refresh mode in response to the control signal refresh. The first switch may include a PMOS transistor P31, and the second switch includes an inverter IV30and a PMOS transistor P32.

The operation of the internal voltage supply circuit with the above-stated configuration according to the second embodiment will hereinafter be described with reference toFIGS. 4 and 6in conjunction with respective operation modes of a semiconductor device.

A description will first be given of the operation of the internal voltage supply circuit in the case where the operation mode of the semiconductor device is the normal mode, namely, an operation mode in which active operations except a refresh operation (i.e., actual operations including a data input operation, a data output operation, etc.) are performed.

In the normal mode, the first internal voltage VINT1is supplied simultaneously to the refresh-associated circuit310and a peripheral circuit320, as shown inFIG. 4. At this time, the switching circuit350acts to switch the first internal voltage VINT1to the refresh-associated circuit310in response to the control signal refresh such that the first internal voltage VINT1is applied to the refresh-associated circuit310in the normal mode. That is, in normal mode, the control signal refresh assumes a low level. Thus, in the switching circuit350, as shown inFIG. 6, the PMOS transistor P31is turned on in response to the control signal refresh and the PMOS transistor P32is turned off in response to the control signal refresh, thereby causing the first internal voltage VINT1to be applied to the refresh-associated circuit310. As a result, in the normal mode, the first internal voltage VINT1is applied to the refresh-associated circuit310such that operations associated with the normal mode are performed.

Here, the control signal refresh indicates that the semiconductor device is in the refresh operation, similarly to that in the first embodiment. Namely, the control signal refresh remains disabled low in level in the normal mode, and is then enabled high in level when the semiconductor device enters the refresh mode. The refresh-associated circuit310and the peripheral circuit320are the same as those in the first embodiment. The first internal voltage generator330is a circuitry for generating the first internal voltage VINT1to be used in the refresh-associated circuit310and the peripheral circuit320when the operation mode of the semiconductor device is the normal mode. The first internal voltage VINT1is generated depending on the external voltage VDD and is higher than the second internal voltage VINT2to be described later.

Next, when the semiconductor device enters refresh mode, the second internal voltage VINT2, not the first internal voltage VINT1, is supplied to the refresh-associated circuit310, as shown inFIGS. 4 and 6. That is, because the control signal refresh makes a low to high level transition in the refresh mode, the output of the inverter IV30becomes low in level to turn on the PMOS transistor P32, whereas the PMOS transistor P31is turned off, as shown inFIG. 6. As a result, the second internal voltage VINT2is applied to the refresh-associated circuit310. Here, the second internal voltage generator340is a circuitry for generating the second internal voltage VINT2for a cell operation such as reading or writing of data from or into a cell. The second internal voltage VINT2is lower than the first internal voltage VINT1. In other words, in the refresh mode, the second internal voltage VINT2lower than the first internal voltage VINT1is applied to the refresh-associated circuit310such that operations associated with the refresh mode are performed.

As described above, according to the second embodiment, in the case where the operation mode of the semiconductor device is the refresh mode, an internal voltage lower than a voltage in the normal mode is supplied, so that current consumption of the semiconductor device can be reduced. In addition, the internal voltage supply circuit according to the second embodiment can realize such a current consumption reduction without employing supplementary circuits for control of the supply voltage and without increasing the layout area and standby current. Therefore, the internal voltage supply circuit according to this embodiment provides an economic advantage in terms of the layout and power efficiency of the semiconductor device.

On the other hand, as shown inFIG. 11, the internal voltage supply circuit according to the second embodiment may further comprise a third internal voltage generator360for supplying a third internal voltage VINT3of the same level as that of the second internal voltage VINT2to the refresh-associated circuit310. The third internal voltage generator360is a circuitry for generating and supplying the third internal voltage VINT3of the same level as that of the second internal voltage VINT2to the refresh-associated circuit310irrespective of the operation mode of the semiconductor device. This third internal voltage generator360acts to prevent noise or bouncing which may occur when the operation mode of the semiconductor device is changed between the normal mode and the refresh mode, and to fill up current when it is insufficient.

As shown inFIG. 7, the first switch of the switching circuit350may include the NMOS transistor N41, and the second switch thereof may include the inverter IV40and NMOS transistor N42. In this case, the control signal refresh assumes a high level in the normal mode, and a low level in the refresh mode.

Alternatively, as shown inFIG. 8, the first switch of the switching circuit350may include the PMOS transistor P51, and the second switch thereof may include the NMOS transistor N51. In this case, the control signal refresh assumes a low level in the normal mode, and a high level in the refresh mode.

As another alternative, as shown inFIG. 9, the first switch of the switching circuit350may include the NMOS transistor N61, and the second switch thereof may include the PMOS transistor P61. In this case, the control signal refresh assumes a high level in the normal mode, and a low level in the refresh mode.

As apparent from the above description, provided is an internal voltage supply circuit for supplying an internal voltage lower than a voltage in a normal mode to circuits of a semiconductor device, particularly circuits associated with a refresh operation, when the semiconductor device is in a refresh mode, thereby reducing current consumption of the semiconductor device.