Level shifting circuit and integrated circuit

1. Technical Field

The instant disclosure relates to a level shifting circuit for shifting a first logic high level of input voltages to generate a second logic high level of output voltages, and to an integrated circuit using the level shifting circuit.

2. Description of Related Art

In modern integrated circuit design, the logical core and the input/output unit may be powered by distinct voltages. For example, in an integrated circuit manufactured by a 0.13 μm process technique, the logical core may be powered by a power of 1.2 volts, and the input/output unit is powered by a power of 3.3 volts. Because signals of the logical core operate within a first voltage range (e.g. 0 through 1.2 volts) and signals of the input/output unit operate within a second voltage range (e.g. 0 through 3.3 volts), a level shifting circuit is generally required to ensure that the signals conveyed between the logical core and the input/output unit are at correct logical states.

Referring to FIG. 1 , FIG. 1 is a circuit diagram showing a conventional level shifting circuit. The conventional level shifting circuit 1 comprises a pair of N-type metal-oxide-semiconductor (NMOS) transistors N 1 , N 2 , and a pair of P-type metal-oxide-semiconductor (PMOS) transistors P 1 , P 2 . The input voltages IN_ 1 and IN_ 2 are input to the conventional level shifting circuit 1 , and the conventional level shifting circuit 1 generates the output voltages OUT_ 1 and OUT_ 2 according to the input voltages IN_ 1 and IN_ 2 , wherein the input voltage IN_ 2 is the inversion of the input voltage IN_ 1 , and the output voltage OUT_ 2 is the inversion of the output voltage OUT_ 1 . A first logic high level of the input voltages IN_ 1 and IN_ 2 is not the same as a second logic high level of the output voltages OUT_ 1 and OUT_ 2 . For example, the first logic high level of the input voltages IN_ 1 and IN_ 2 is 1.2 volts, and the second logic high level of the output voltages OUT_ 1 and OUT_ 2 is 3.3 volts. That is, the conventional level shifting circuit 1 shifts first logic high level of the input voltages IN_ 1 and IN_ 2 to the second logic high level of the output voltages OUT_ 1 and OUT_ 2 so as to generate the output voltages OUT_ 1 and OUT_ 2 .

The details of the circuit structure associated with the conventional level shifting circuit 1 are illustrated as follows. Source ends of the NMOS transistors N 1 and N 2 are connected to a low voltage with a logic low level, such as ground voltage GND. Gate ends of the NMOS transistors N 1 and N 2 respectively receive the input voltages IN_ 1 and IN_ 2 . A drain end of the PMOS transistor P 1 is connected to a drain end of the NMOS transistor N 1 and a gate end the PMOS transistor P 2 , and a drain end of the PMOS transistor P 2 is connected to a drain end of the NMOS transistor N 2 and a gate end the PMOS transistor P 1 . Source ends of the PMOS transistors P 1 and P 2 are connected to a high voltage with the second logic high level, such as system voltage VDD. The drain end of the PMOS transistor P 2 is used to deliver the output voltage OUT_ 1 , and the drain end of the PMOS transistor P 1 is used to deliver the output voltage OUT_ 2 .

By above circuit structure of the conventional level shifting circuit 1 , in a first situation, during a transient period, when the input voltage IN_ 1 changes to the first logic high level from the logic low level, and the input voltage IN_ 2 changes to the logic low level from the first logic high level, the NMOS transistor N 1 is turned on, and the NMOS transistor N 2 is turned off. Since the NMOS transistor N 1 is turned on, the output voltage OUT_ 2 is pulled down to the ground voltage GND from the second logic high level (i.e. VDD), and then the PMOS transistor P 2 is turned on when the output voltage OUT_ 2 has decreased to the level which the system voltage subtracts a threshold voltage VTP of the PMOS transistor P 2 . Since the PMOS transistor P 2 is turned on, the output voltage OUT_ 1 is pushed up to the system voltage VDD with the second logic high level from the ground voltage GND (i.e. the logic low level), and the PMOS transistor P 1 is turned off when the output voltage OUT_ 1 has increased to the level which the system voltage subtracts a threshold voltage VTP of the PMOS transistor P 1 (i.e. VDD−VTP). After the output voltage OUT_ 1 is equal to the system voltage VDD and the output voltage OUT_ 2 is equal to the ground voltage GND, the transient period elapses and a steady period begins.

In the first situation, during the steady period, a drain-source voltage of the NMOS transistor N 2 being turned off is the system voltage VDD, a gate-source voltage of the NMOS transistor N 1 being turned on is the first logic high level, a drain-source voltage of the PMOS transistor P 1 being turned off is the system voltage VDD, and a gate-source voltage of the PMOS transistor P 2 being turned on is the system voltage VDD. The PMOS transistor P 1 suffers the high drain-source voltage, the PMOS transistor P 2 suffers the high gate-source voltage, and the NMOS transistor N 2 suffers the high drain-source voltage, such that the PMOS transistors P 1 , P 2 and the NMOS transistor N 2 have large damage probability, or lifetimes of the PMOS transistors P 1 , P 2 and the NMOS transistor N 2 may be reduced.

It is noted that, in the first situation, during the transient period, before the output voltage OUT_ 1 has increased to the level which the system voltage VDD subtracts the threshold voltage VTP of the PMOS transistor P 1 (i.e. VDD−VTP), the PMOS transistor P 1 is not turned off and the NMOS transistor N 1 is turned on, such that the output voltage OUT_ 2 cannot be rapidly pulled down to the ground voltage GND, and the output voltage OUT_ 1 cannot be rapidly pushed up to the system voltage VDD with the second logic high level.

In a second situation, during a steady period, the input voltage IN_ 2 has first logic high level and the input voltage IN_ 1 has the logic low level, the NMOS transistor N 2 and the PMOS transistor P 1 are turned on, and the NMOS transistor N 1 and the PMOS transistor P 2 are turned off, such that the output voltage OUT_ 2 is the system voltage VDD with the second logic high level, and the output voltage OUT_ 1 is the ground voltage GND with the logic low level. The PMOS transistor P 2 suffers the high drain-source voltage, the PMOS transistor P 1 suffers the high gate-source voltage, and the NMOS transistor N 1 suffers the high drain-source voltage, such that the PMOS transistors P 1 , P 2 and the NMOS transistor N 1 have large damage probability, or lifetimes of the PMOS transistors P 1 , P 2 and the NMOS transistor N 1 may be reduced.

It is noted that, in the second situation, during a transient period, before the output voltage OUT_ 2 is increased to the level which the system voltage VDD subtracts the threshold voltage of the PMOS transistor P 2 (i.e. VD−VTP), the PMOS transistor P 2 is not turned off, and the NMOS transistor N 2 is turned on, such that the output voltage OUT_ 1 cannot be rapidly pulled down to the ground voltage GND, and the output voltage OUT_ 2 cannot be rapidly pushed up to the system voltage VDD with the second logic high level.

A common manner for solving the problem of a low operation speed in both of the first and second situations is to increase channel lengths of the PMOS transistors P 1 and P 2 . However, this common manner increases a size of the conventional level shifting circuit 1 .

An exemplary embodiment of the instant disclosure provides a level shifting circuit, and the level shifting circuit comprises a first through fourth NMOS transistors and a first through fourth PMOS transistors. The first NMOS transistor has a gate end for receiving a first input voltage, a source end connected to a first logic low level, and a drain end. The second NMOS transistor has a gate end for receiving a second input voltage, a source end connected to the first logic low level, and a drain end, wherein the second input voltage is an inversion of the first input voltage. The third NMOS transistor has a gate end connected to a first logic high level, a source end connected to the drain end of the first NMOS transistor, and a drain end. The fourth NMOS transistor has a gate end connected to the first logic high level, a source end connected to the drain end of the second NMOS transistor, and a drain end. The first PMOS transistor has a gate end, a source end connected to a second logic high level, and a drain end. The second PMOS transistor has a gate end, a source end connected to the second logic high level, and a drain end, wherein the drain end of the second PMOS transistor is connected to the gate end of the first PMOS transistor and used to deliver a first output voltage, the drain end of the first PMOS transistor is connected to the gate end of the second PMOS transistor and used to deliver a second output voltage, and the second output voltage is an inversion of the first output voltage. The third PMOS transistor has a gate end for receiving the second input voltage, a source end connected to the drain end of the first PMOS transistor, and a drain end connected to the drain end of the third NMOS transistor. The fourth PMOS transistor has a gate end for receiving the first input voltage, a source end connected to the drain end of the second PMOS transistor, and a drain end connected to the drain end of the fourth NMOS transistor.

An exemplary embodiment of the instant disclosure provides an integrated circuit. The integrated circuit comprises a first block utilizing the first logic high level for presenting logic 1, a second block utilizing the second logic high level for presenting logic 1, and the above level shifting circuit. The level shifting circuit connected between the first block and the second block is used to shift the first logic high level to the second logic high level.

The level shifting circuit and the integrated circuit provided in the exemplary embodiments of the present disclosure have the high operation speed, the long lifetime, and the low damage probability.

For further understanding of the instant disclosure, reference is made to the following detailed description illustrating the embodiments of the instant disclosure. The description is only for illustrating the instant disclosure, not for limiting the scope of the claim.

Embodiments are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings, in which like references indicate similar elements and in which:

FIG. 1 is a circuit diagram showing a conventional level shifting circuit;

FIG. 2 is a circuit diagram showing a level shifting circuit according to an exemplary embodiment of the present disclosure; and

FIG. 3 is a block diagram showing an integrated circuit according to an exemplary embodiment of the present disclosure.

The aforementioned illustrations and following detailed descriptions are exemplary for the purpose of further explaining the scope of the instant disclosure. Other objectives and advantages related to the instant disclosure will be illustrated in the subsequent descriptions and appended drawings.

It will be understood that, although the terms first, second, third, and the like, may be used herein to describe various elements, but these elements should not be limited by these terms. These terms are only to distinguish one element from another region or section discussed below could be termed a second element without departing from the teachings of the instant disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Exemplary Embodiment of Level Shifting Circuit

In one exemplary embodiment of the present disclosure, a level shifting circuit is provided. Compared to the conventional level shifting circuit, the level shifting circuit herein further has another pair of PMOS transistors and another pair of NMOS transistors, wherein the other pair of the PMOS transistors is connected to the pair of the PMOS transistors, and the other pair of the NMOS transistors is connected to the pair of the NMOS transistors.

The other pair of the PMOS transistors and the other pair of the NMOS transistors can reduce the drain-source voltages and the gate-source voltage of the pair of the PMOS transistors, and reduce the drain-source voltages of the pair of the NMOS transistors. Furthermore, the drain-source voltages and the gate-source voltages of the other pair of the PMOS transistors and the other pair of the NMOS transistors are not large. Therefore, plurality of PMOS transistors and plurality of NMOS transistors in the level shifting circuit are protected, the lifetime of the level shifting circuit is increased, and the damage probability of the level shifting circuit is decreased.

It is noted that by the circuit structure of the level shifting circuit according to the exemplary embodiment of the present disclosure, the other pair of the PMOS transistors being turned on can be operated in the saturation region rather than in the linear region, such that the operation speed of the level shifting circuit is enhanced.

Moreover, the level shifting circuit further comprises an output stage circuit, wherein the output stage circuit comprises two PMOS transistors and a NMOS transistor. In the output stage circuit, the two PMOS transistors are serially connected to each other, one of the two PMOS transistors acts as a diode, and the NMOS transistor is connected to the PMOS transistor acting as the diode. One of two input voltages is input to a gate end of the NMOS transistor in the output stage circuit, and a gate end of the PMOS transistor not acting as the diode in the output stage circuit is connected to a drain end of corresponding one PMOS transistor in the pair of the PMOS transistors. Additionally, an output capacitor can be disposed between the connection point of the two PMOS transistors of the output stage circuit and a ground voltage.

Please refer to FIG. 2 . FIG. 2 is a circuit diagram showing a level shifting circuit according to an exemplary embodiment of the present disclosure. The level shifting circuit 2 comprises a level shifting unit 21 , an output stage circuit 22 , and an output capacitor C_OUT. The output stage circuit 22 is connected to the level shifting unit 21 and the output capacitor C_OUT. It is noted that the output stage circuit 22 and the output stage circuit 22 can be removed therefrom in one other exemplary embodiment, and that is, the output stage circuit 22 and the output stage circuit 22 are not essential components of the level shifting circuit 2 .

The level shifting unit 21 receives the input voltages IN_ 1 and IN_ 2 , and the input voltage IN_ 2 is the inversion of the input voltage IN_ 1 . A first logic high level of the input voltages IN_ 1 and IN_ 2 is a level of a voltage VD. The level shifting unit 21 is used to shift the first logic high level to a second logic high level of the output voltages OUT_ 1 and OUT_ 2 , and to deliver the output voltage OUT_ 1 and OUT_ 2 , wherein the second logic high level can be a level of a system voltage VDD, and the output voltage OUT_ 2 is the inversion of the output voltage OUT_ 1 . The output stage circuit 22 receives the output voltage OUT_ 2 and the input voltage IN_ 2 to generate an output voltage OUT_ 3 across the output capacitor C_OUT. Furthermore, the first logic low level of the input voltages IN_ 1 and IN_ 2 is not same as the second logic low level of the output voltages OUT_ 1 and OUT_ 2 .

The level shifting unit 21 comprises a first pair of PMOS transistors P 1 , P 2 , a second pair of PMOS transistors P 3 , P 4 , a first pair of NMOS transistors N 1 , N 2 , and a second pair of NMOS transistors N 3 , N 4 . The first pair of the PMOS transistors P 1 , P 2 is connected to the second pair of the PMOS transistors P 3 , P 4 , the second pair of the PMOS transistors P 3 , P 4 is connected to the second pair of the NMOS transistors N 3 , N 4 , and the second pair of the NMOS transistors N 3 , N 4 is connected to the first pair of the NMOS transistors N 1 , N 2 . That is, the first pair of PMOS the transistors P 1 , P 2 , the second pair of PMOS the transistors P 3 , P 4 , the second pair of the NMOS transistors N 3 , N 4 , and the first pair of the NMOS transistors N 1 , N 2 are disposed in a serial connection.

The first pair of the PMOS transistors P 1 , P 2 acts as a latch, and generates the output voltages OUT_ 2 and OUT_ 1 at drain ends of first pair of the PMOS transistors P 1 , P 2 . The second pair of PMOS the transistors P 3 , P 4 , receive the input voltages IN_ 2 and IN_ 1 , and the first pair of the NMOS transistors N 1 , N 2 receive the input voltage IN_ 1 and IN_ 2 . The second pair of the NMOS transistors N 3 , N 4 receives the voltage VD with the first logic high level.

In a first situation, when the input voltage IN_ 1 changes to the first logic high level from a first logic low level, the output voltage OUT_ 1 is pushed up to the system voltage VDD with the second logic high level from a threshold voltage VTP of the PMOS transistor P 4 . In a second situation, when the input voltage IN_ 2 changes to the first logic high level from a first logic low level, the output voltage OUT_ 2 is pushed up to the system voltage VDD with the second logic high level from a threshold voltage VTP of the PMOS transistor P 3 .

Specifically, a gate end of the NMOS transistor N 1 receives the input voltage IN_ 1 , and a gate end of the NMOS transistor N 2 receives the input voltage IN_ 2 . Source ends of the NMOS transistors N 1 and N 2 are connected to a low voltage with the first logic low level, such as the ground voltage GND. A drain end of the NMOS transistor N 1 is connected to a source end of the NMOS transistor N 3 , and a drain end of the NMOS transistor N 2 is connected to a source end of the NMOS transistor N 4 . The gate ends of the NMOS transistors N 3 and N 4 receive the voltage VD with the first logic high level.

A drain end of the NMOS transistor N 3 is connected to a drain end of the PMOS transistor P 3 , and a drain end of the NMOS transistor N 4 is connected to a drain end of the PMOS transistor P 4 . The gate end of the PMOS transistor P 3 receives the input voltage IN_ 2 , and the gate end of the PMOS transistor P 4 receives the input voltage IN_ 1 . A source end of the PMOS transistor P 3 is connected to the drain end of the PMOS transistor P 1 , and a source end of the PMOS transistor P 4 is connected to the drain end of the PMOS transistor P 2 .

A gate end of the PMOS transistor P 2 is connected to the drain end of the PMOS transistor P 1 , and a gate end of the PMOS transistor P 1 is connected to the drain end of the PMOS transistor P 2 . The output voltages OUT_ 1 and OUT_ 2 are delivered from the drain ends of the PMOS transistors P 2 and P 1 respectively. Source ends of the PMOS transistors P 1 and P 2 are connected to the system voltage VDD with the second logic high level. Body ends of the NMOS transistors N 1 through N 4 are connected to the ground voltage GND. Body ends of the PMOS transistors P 1 through P 4 are connected to the system voltage VDD with the second logic high level.

By the circuit structure of the level shifting unit 21 , in the first situation, during a transient period, when the input voltage IN_ 1 changes to the first logic high level (i.e. the level of the voltage VD) from the first logic low level (i.e. the level of the ground voltage GND) and the input voltage IN_ 2 changes to the first logic low level from the first logic high level, the NMOS transistor N 1 is turned on, and the NMOS transistor N 2 is turned off. Meanwhile, the NMOS transistor N 3 and the PMOS transistor P 3 is turned on, thus the voltage at the drain end of the NMOS transistor N 1 (or the voltage at the source end of the NMOS transistor N 3 ) is pulled down to the ground voltage GND from a level which the first logic high level subtracts a threshold voltage VTN of the NMOS transistor N 3 (i.e. VD−VTN), the voltage at the drain ends of the PMOS transistor P 3 and the NMOS transistor N 3 is pulled down to the ground voltage GND from the system voltage VDD, and the output voltage OUT_ 2 is pulled down to the threshold voltage VTP of the PMOS transistor P 3 from the system voltage VDD.

When the output voltage OUT_ 2 has decreased to a level which the system voltage VDD subtracts a threshold voltage VTP of the PMOS transistor P 2 (i.e. VDD−VTP), the PMOS transistor P 2 is turned on, and then the output voltage OUT_ 1 is pushed up to the system voltage VDD with the second logic high level from a threshold voltage VTP of the PMOS transistor P 4 .

When the output voltage OUT_ 1 has increased to a level which the first logic high level adds the threshold voltage VTP of the PMOS transistor P 4 (i.e. VD+VTP), the PMOS transistor P 4 and the NMOS transistor N 4 are turned on, such that the voltage at the drain ends of the NMOS transistor N 4 and the PMOS transistor P 4 is pushed up to the system voltage VDD from the ground voltage GND, and the voltage at the source end of the NMOS transistor N 4 (or the voltage at the drain end of the NMOS transistor N 2 ) is pushed up to the first logic high level minus a threshold voltage VTN of the NMOS transistor N 4 (i.e. VD−VTN) from the ground voltage GND.

When the output voltage OUT_ 1 has increased to a level which the system voltage VDD subtracts a threshold voltage VTP of the PMOS transistor P 1 (i.e. VDD−VTP), the PMOS transistor P 1 is turned off. After the output voltage OUT_ 2 is equal to the threshold voltage VTP of the PMOS transistor P 3 and the output voltage OUT_ 1 is equal to the system voltage VDD with second logic high level, the transient period elapses, and a steady period begins.

In the first situation, during the steady period, the output voltages OUT_ 2 and OUT_ 1 are equal to the threshold voltage VTP of the PMOS transistor P 3 (i.e. the second logic low level) and the system voltage VDD with second logic high level respectively, the voltage at the drain end of the PMOS transistor P 3 (or the voltage at the drain end of the voltage at the NMOS transistor N 3 ) is equal to the ground voltage GND, and the voltage at the source end of the NMOS transistor N 3 (or the voltage at the drain end of the NMOS transistor N 1 ) is also equal to the ground voltage GND. The voltage at the drain end of the PMOS transistor P 4 (or the voltage at drain end of the NMOS transistor N 4 ) is equal to the lager one of the system voltage VDD and the first logic high level added with threshold voltage VTP of the PMOS transistor P 4 ; that is, Max (VDD, VD+VTP). The voltage at the source end of the NMOS transistor N 4 (or the voltage at the drain end of the NMOS transistor N 2 ) is equal to the level which the first logic high level subtracts the threshold voltage VTN of the NMOS transistor N 4 (VD−VTN). In practice, the difference between the first logic high level VDD and the second logic high level VD is much larger than the threshold voltage VTP. In other words, VDD>>VD+VTP, and thus VDD=Max (VDD, VD+VTP).

In the first situation, during the steady period, a drain-source voltage of the PMOS transistor P 1 being turned off is the level which the system voltage VDD subtracts the threshold voltage VTP of the PMOS transistor P 3 (i.e. VDD−VTP), and a gate-source voltage of the PMOS transistor P 2 being turned on is the level which the system voltage VDD subtracts the threshold voltage VTP of the PMOS transistor P 3 (i.e. VDD−VTP). A drain-source voltage and a gate-source voltage of the PMOS transistor P 3 being turned on are the threshold voltage VTP of the PMOS transistor P 3 , and a drain-source voltage and a gate-source voltage of the PMOS transistor P 4 being turned on are respectively 0 and the level which the system voltage VDD subtracts the first logic high level (i.e. VDD−VD).

A drain-source voltage of the NMOS transistor N 3 being turned on is 0, and a gate-source voltage of the NMOS transistor N 3 being turned on is the first logic high level (i.e. VD). A drain-source voltage of the NMOS transistor N 4 being turned on is the level which the system voltage VDD subtracts first logic high level and adds the threshold voltage VTN of the NMOS transistor N 4 (i.e. VDD−(VD−VTN)), and a gate-source voltage of the NMOS transistor N 4 being turned on is the threshold voltage VTN of the NMOS transistor N 4 . A drain-source voltage of the NMOS transistor N 1 being turned on is 0, and a gate-source voltage of the NMOS transistor N 1 being turned on is the first logic high level (i.e. VD). A drain-source voltage of the NMOS transistor N 2 being turned off is a level which the first logic high level subtracts the threshold voltage VTN of the NMOS transistor N 4 (i.e. VD−VTN), and a gate-source voltage of the NMOS transistor N 2 being turned off is 0.

In the second situation, during a transient period, the input voltage IN_ 2 changes to the first logic high level (i.e. the level of the voltage VD) from the first logic low level (i.e. the level of the ground voltage GND) and the input voltage IN_ 1 changes to the first logic low level from the first logic high level, the NMOS transistor N 2 is turned on, and the NMOS transistor N 1 is turned off. Meanwhile, the NMOS transistor N 4 and the PMOS transistor P 4 is turned on, thus the voltage at the drain end of the NMOS transistor N 2 (or the voltage at the source end of the NMOS transistor N 4 ) is pulled down to the ground voltage GND from the voltage with the level which the first logic high level subtracts a threshold voltage VTN of the NMOS transistor N 4 (i.e. VD−VTN), the voltage at the drain ends of the PMOS transistor P 4 and the NMOS transistor N 4 is pulled down to the ground voltage GND from the system voltage VDD, and the output voltage OUT_ 1 is pulled down to the threshold voltage VTP of the PMOS transistor P 4 from the system voltage VDD.

When the output voltage OUT_ 1 has decreased to a level which the system voltage VDD subtracts a threshold voltage VTP of the PMOS transistor P 1 (i.e. VDD−VTP), the PMOS transistor P 1 is turned on, and then the output voltage OUT_ 2 is pushed up to the system voltage VDD with the second logic high level from a threshold voltage VTP of the PMOS transistor P 3 .

When the output voltage OUT_ 2 has increased to a level which the first logic high level adds the threshold voltage VTP of the PMOS transistor P 3 (i.e. VD+VTP), the PMOS transistor P 3 and the NMOS transistor N 3 are turned on, such that the voltage at the drain ends of the NMOS transistor N 3 and the PMOS transistor P 3 is pushed up to the system voltage VDD from the ground voltage GND, and the voltage at the source end of the NMOS transistor N 3 (or the voltage at the drain end of the NMOS transistor N 1 ) is pushed up to the first logic high level minus a threshold voltage VTN of the NMOS transistor N 3 (i.e. VD−VTN) from the ground voltage GND.

When the output voltage OUT_ 2 has increased to a level which the system voltage VDD subtracts a threshold voltage VTP of the PMOS transistor P 2 (i.e. VDD−VTP), the PMOS transistor P 2 is turned off. After the output voltage OUT_ 1 is equal to the threshold voltage VTP of the PMOS transistor P 4 and the output voltage OUT_ 2 is equal to the system voltage VDD with second logic high level, the transient period elapses, and a steady period begins.

In the second situation, during the steady period, the output voltages OUT_ 1 and OUT_ 2 are equal to the threshold voltage VTP of the PMOS transistor P 4 (i.e. the second logic low level) and the system voltage VDD with second logic high level respectively, the voltage at the drain end of the PMOS transistor P 4 (or the voltage at the drain end of the NMOS transistor N 4 ) is equal to the ground voltage GND, and the voltage at the source end of the NMOS transistor N 4 (or the voltage at the drain end of the NMOS transistor N 2 ) is also equal to the ground voltage GND. The voltage at the drain end of the PMOS transistor P 3 (or the voltage at drain end of the NMOS transistor N 3 ) is equal to the system voltage VDD, and the voltage at the source end of the NMOS transistor N 3 (or the voltage at the drain end of the NMOS transistor N 1 ) is equal to the level which the first logic high level subtracts the threshold voltage VTN of the NMOS transistor N 3 (VD−VTN).

In the second situation, during the steady period, a drain-source voltage of the PMOS transistor P 2 being turned off is the level which the system voltage VDD subtracts the threshold voltage VTP of the PMOS transistor P 4 (i.e. VDD−VTP), and a gate-source voltage of the PMOS transistor P 1 being turned on is the level which the system voltage VDD subtracts the threshold voltage VTP of the PMOS transistor P 4 (i.e. VDD−VTP). A drain-source voltage and a gate-source voltage of the PMOS transistor P 4 being turned on are the threshold voltage VTP of the PMOS transistor P 4 , and a drain-source voltage and a gate-source voltage of the PMOS transistor P 3 being turned on are respectively 0 and the level which the system voltage VDD subtracts the first logic high level (i.e. VDD−VD).

A drain-source voltage of the NMOS transistor N 4 being turned on is 0, and a gate-source voltage of the NMOS transistor N 4 being turned on is the first logic high level (i.e. VD). A drain-source voltage of the NMOS transistor N 3 being turned on is the level which the system voltage VDD subtracts first logic high level and adds the threshold voltage VTN of the NMOS transistor N 3 (i.e. VDD−(VD−VTN)), and a gate-source voltage of the NMOS transistor N 3 being turned on is the threshold voltage VTN of the NMOS transistor N 3 . A drain-source voltage of the NMOS transistor N 2 being turned on is 0, and a gate-source voltage of the NMOS transistor N 2 being turned on is the first logic high level (i.e. VD). A drain-source voltage of the NMOS transistor N 1 being turned off is a level which the first logic high level subtracts the threshold voltage VTN of the NMOS transistor N 3 (i.e. VD−VTN), and a gate-source voltage of the NMOS transistor N 1 being turned off is 0.

It is obvious that, by the circuit structure of the level shifting unit 21 , the drain-source voltages and the gate-source voltages suffered by the PMOS transistors P 1 and P 2 can be reduced, and the drain-source voltages suffered by the NMOS transistors N 1 and N 2 can be also reduced. Furthermore, the gate-source voltages and the drain-source voltages suffered by the NMOS transistors N 3 , N 4 , and the PMOS transistors P 3 , P 4 are not large. Therefore, the level shifting unit 21 makes the level shifting circuit 2 has large life time and low damage probability. Moreover, the NMOS transistors N 3 and N 4 are operated in the saturation region rather than the linear region, and one of the PMOS transistors P 3 and P 4 is also operated in the saturation region, therefore increasing the operation speed of the level shifting unit 21 and the level shifting circuit 2 .

The output stage circuit 22 comprises two PMOS transistors P 5 , P 6 , and a NMOS transistor N 5 . A source end of the PMOS transistor P 5 is connected to the system voltage VDD, a gate end of the PMOS transistor P 5 receives the output voltage OUT_ 2 , and a drain end of the PMOS transistor P 5 is connected to a source end of the PMOS transistor P 6 . A gate end of the PMOS transistor P 6 is connected to a drain end of the PMOS transistor P 6 , and the drain end of the PMOS transistor P 6 is connected to drain end of the NMOS transistor N 5 . A gate end of the NMOS transistor N 5 receives the input voltage IN_ 2 , and a source end of the NMOS transistor N 5 is connected to the ground voltage GND. Body ends of the PMOS transistors P 5 and P 6 are connected to the system voltage VDD, and a body end of the NMOS transistor N 5 is connected to the ground voltage GND. One end of output capacitor C_OUT is connected to the source end of the PMOS transistor P 6 and the drain end of the PMOS transistor P 5 , and other one end of the output capacitor C_OUT is connected to the ground voltage GND.

In the first situation, during the transient period, the NMOS transistor N 5 is turned off, and the PMOS transistor P 6 is turned on and acting as the diode. When the output voltage OUT_ 2 has decreased to the level which the system voltage VDD subtracts the threshold voltage VTP of the PMOS transistor P 5 (i.e. VDD−VTP), the PMOS transistor P 5 is turned on. The output voltage OUT_ 3 is pulled to the system voltage VDD from the threshold voltage VTP of the PMOS transistor P 6 (i.e. the second logic low level), and the voltage at the drain ends of the PMOS transistor P 6 and the NMOS transistor N 5 is pulled to the system voltage VDD minus the threshold voltage of the PMOS transistor P 6 (i.e. VDD−VTP) from the ground voltage GND. During the steady period, the output voltage OUT_ 3 is equal to the system voltage VDD with the second logic high level, and the voltage at the drain ends of the PMOS transistor P 6 and the NMOS transistor N 5 is equal to the system voltage VDD minus the threshold voltage of the PMOS transistor P 6 .

In the second situation, during the transient period, the NMOS transistor N 5 is turned on, and the PMOS transistor P 6 is turned on and acting as the diode. When the output voltage OUT_ 2 has increased to the level which the system voltage VDD subtracts the threshold voltage VTP of the PMOS transistor P 5 (i.e. VDD−VTP), the PMOS transistor P 5 is turned off. The output voltage OUT_ 3 is pulled down to the threshold voltage VTP of the PMOS transistor P 6 from the system voltage VDD, and the voltage at the drain ends of the PMOS transistor P 6 and the NMOS transistor N 5 is pulled down ground voltage GND from the system voltage VDD minus the threshold voltage of the PMOS transistor P 6 (i.e. VDD−VTP). During the steady period, the output voltage OUT_ 3 is equal to the threshold voltage VTP of the PMOS transistor P 6 (i.e. the second logic low level), and the voltage at the drain ends of the PMOS transistor P 6 and the NMOS transistor N 5 is equal to ground voltage GND.

In short, the output stage circuit 22 acts as a buffer for buffering the output voltage OUT_ 2 . Moreover, during the steady period of the first situation or the second situation, the gate-source voltage and the drain-source of the PMOS transistor P 6 are the threshold voltage VTP of the PMOS transistor P 6 . During the steady period of the first situation, the drain-source voltage and the gate-source voltage of PMOS transistor P 5 being turned on are respectively 0 and the system voltage VDD minus the threshold voltage VTP of the PMOS transistor P 3 (i.e. VDD−VTP), and the drain-source voltage and the gate-source voltages of NMOS transistor N 5 being turned off are respectively the system voltage VDD minus the threshold voltage VTP of the PMOS transistor P 6 (i.e. VDD−VTP) and 0. During the steady period of the second situation, the drain-source voltage and the gate-source voltages of PMOS transistor P 5 being turned off are respectively the system voltage VDD minus the threshold voltage VTP of the PMOS transistor P 6 and 0, and the drain-source voltage and the gate-source voltages of NMOS transistor N 5 being turned on are respectively 0 and the first logic high level (i.e. VD).

That is, the drain-source voltage and the gate-source voltage suffered by the PMOS transistors P 5 can be reduced, the drain-source voltage suffered by the NMOS transistor N 5 can be reduced, and the PMOS transistor P 6 suffers the low drain-source voltage and gate-source voltage. Therefore, the output stage circuit 21 has the long lifetime, and the low damage probability.

Exemplary Embodiment of Integrated Circuit

The above level shifting circuit can be used in an integrated circuit needing signals with different logic high levels, and the integrated circuit can be a memory integrated circuit, an audio processing integrated circuit, or other integrated circuit, for example. That is, the level shifting circuit shifts the first logic high level of one block to the second logic high level of the other one block, and vice versa. The two blocks can be a logic core and an input/output unit, but the present disclosure is not limited thereto.

Please refer to FIG. 3 . FIG. 3 is a block diagram showing an integrated circuit according to an exemplary embodiment of the present disclosure. The integrated circuit 3 comprises a logic core 31 , a level shifting circuit 32 , and an input/output unit 33 . The level shifting circuit 32 is connected between the logic core 31 and the input/output unit 33 . The logic core 31 utilizes a first logic high level for presenting logic 1, and the input/output unit 33 utilizes a second logic high level for presenting logic 1, wherein the first logic high level is not the same as the second logic high level, and the first logic high level and the second logic high level for example can be 1.2 volts and 3.3 volts respectively while the integrated circuit 3 is manufactured by the 0.13 μm process technique.

The level shifting circuit 32 can be one of the level shifting circuit mentioned above, and is used to shift the first logic high level of logic core 31 to the second logic high level of the input/output unit 33 , or shift the second logic high level of the input/output unit 33 to the first logic high level of logic core 31 . Therefore, the signals conveyed between the logical core 31 and the input/output unit 33 can be at correct logical states. Moreover, as mentioned above, the level shifting circuit 32 has the high operation speed, the long lifetime, and the low damage probability, thus the integrated circuit 3 also has the high operation speed, the long lifetime, and the low damage probability.

To sum up, the level shifting circuit and the integrated circuit provided in the exemplary embodiments of the present disclosure has the high operation speed, the long lifetime, and the low damage probability, since plurality of NMOS transistors and plurality PMOS transistors therein are protected, and some NMOS transistors therein are operated in the saturation region rather than the linear region.

The descriptions illustrated supra set forth simply the preferred embodiments of the instant disclosure; however, the characteristics of the instant disclosure are by no means restricted thereto. All changes, alterations, or modifications conveniently considered by those skilled in the art are deemed to be encompassed within the scope of the instant disclosure delineated by the following claims.