Level shifter

• US 20060208759A1
• Filed: 03/16/2006
• Published: 09/21/2006
• Est. Priority Date: 03/16/2005
• Status: Active Grant

• Current Assignee: Socionext Inc.
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Nojiri, Naoki
• Granted Patent: US 7,348,801 B2
• Time in Patent Office: Days
• US Class Current: 326/81
• CPC Class Codes: H03K 17/162 without feedback from the output circuit to the control circuit
• CPC Class Codes: H03K 3/012 Modifications of generator to improve response time or to decrease power consumption
• CPC Class Codes: H03K 3/013 Modifications of generator to prevent operation by noise or interference
• CPC Class Codes: H03K 3/356113 using additional transistors in the input circuit

Abstract

In a level shifter, OFF leakage currents flow through two N-type transistors for signal input even when they are OFF. However, another N-type transistor serving as an OFF leakage generation circuit and three P-type transistors serving as current mirrors, which constitute a current conversion circuit, supply to the signal-input transistors a current equivalent to or greater than the OFF leakage currents flowing through the signal-input transistors when they are OFF, thereby canceling the OFF leakage currents. Therefore, one of nodes which is at H level is surely fixed to a potential equal to a higher voltage supply. Thus, the level shifter surely operates with a high speed even when large OFF leakage currents flow through the signal-input transistors.

Claims

1. A level shifter, comprising:

first and second first-conductivity type transistors for signal input, the first and second first-conductivity type transistors respectively receiving at gates complementary first and second input signals generated using a first voltage supply as a power supply and having ends connected to a ground and the other ends connected to first and second nodes, respectively;

a power supply circuit having an end connected to a second voltage supply and the other end connected to the first and second nodes, the power supply circuit supplying a voltage of the second voltage supply to one of the first and second nodes while interrupting the supply of the voltage of the second voltage supply to the other node;

an OFF leakage generation circuit formed by a third first-conductivity type transistor which has an end and gate connected to the ground and the other end connected to the third node; and

a current conversion circuit connected to the third node to convert a current flowing through the third first-conductivity type transistor to a current flowing from the second voltage supply and amplify the converted current by a predetermined factor, the amplified current being output to the first and second nodes.

2. The level shifter of claim 1, wherein the current conversion circuit is a current mirror formed by a second-conductivity type transistor.

3. The level shifter of claim 1, further comprising a switch circuit between the output of the current conversion circuit and the first and second nodes, the switch circuit being controlled based on the potentials of the first and second nodes to supply the output current of the current conversion circuit to any one of the first and second nodes.

4. The level shifter of claim 3, wherein:

when one of the first and second nodes is equal in potential to the second voltage supply, the switch circuit disconnects the output of the current conversion circuit from the other node; and

when the one of the first and second nodes is equal in potential to the ground, the switch circuit connects the output of the current conversion circuit to the other node.

5. The level shifter of claim 1, wherein:

the output of the current conversion circuit is provided between the second voltage supply and the power supply circuit; and

the switch circuit is realized by the power supply circuit.

6. The level shifter of claim 1, wherein:

the power supply circuit includes cross-coupled first and second second-conductivity type transistors having ends connected to the second voltage supply and the other ends connected to the first and second nodes, respectively;

the level shifter includes a current interrupter for interrupting a through current by disconnecting the second voltage supply from the first or second second-conductivity type transistor when the levels of the input signals change; and

the output of the current conversion circuit is output to a connection point of the power interrupter and the first and second second-conductivity type transistors.

12. The level shifter of claim 1, wherein the first, second and third first-conductivity type transistors are set to have a same threshold voltage which is lower than those of the other transistors.

14. The level shifter of claim 1, further comprising:

a first first-conductivity type high voltage transistor provided between the first first-conductivity type transistor and the first node;

a second first-conductivity type high voltage transistor provided between the second first-conductivity type transistor and the second node; and

a third first-conductivity type high voltage transistor provided between the third first-conductivity type transistor and the third node,

wherein the first, second and third first-conductivity type transistors are formed by low voltage transistors, and

gates of the first, second and third first-conductivity type high voltage transistors are controlled such that a potential equal to or greater than a peak inverse voltage of the low voltage transistor is prevented from being input to the first, second and third first-conductivity type transistors.

16. The level shifter of claim 14, wherein:

the gate of the first first-conductivity type high voltage transistor is connected to a gate of the first first-conductivity type transistor;

the gate of the second first-conductivity type high voltage transistor is connected to a gate of the second first-conductivity type transistor; and

the gate of the third first-conductivity type high voltage transistor is connected to the ground.

18. The level shifter of claim 1, wherein the current conversion circuit outputs a current equivalent to or greater than an OFF leakage current generated when the first and second first-conductivity type transistors are OFF.

20. The level shifter of claim 1, further comprising a resistor between the third node and the ground.

21. The level shifter of claim 1, further comprising a disconnection circuit, wherein

when the first voltage supply is shut down, the disconnection circuit disconnects the OFF leakage generation circuit from the current conversion circuit while stopping a level shift function.

22. A level shift device, comprising a plurality of level shifters, each of which is the level shifter of claim 2,

wherein the OFF leakage generation circuit included in each of the level shifters and a second-conductivity type transistor for generating a bias potential of a current mirror are shared among the plurality of level shifters.

7. A level shifter, comprising:

first and second first-conductivity type transistors for signal input, the first and second first-conductivity type transistors respectively receiving at gates complementary first and second input signals generated using a first voltage supply as a power supply and having ends connected to a ground and the other ends connected to first and second nodes, respectively;

cross-coupled first and second second-conductivity type transistors having ends connected to a second voltage supply and the other ends connected to the first and second nodes, respectively;

a third second-conductivity type transistor provided between the first node and the gate of the second second-conductivity type transistor;

a fourth second-conductivity type transistor provided between the second node and the gate of the first second-conductivity type transistor;

third and fourth first-conductivity type transistors for signal input, receiving the first and second input signals, respectively, at gates and having ends connected to the ground and the other ends connected to gates of the second and first second-conductivity type transistors, respectively;

an OFF leakage generation circuit formed by a fifth first-conductivity type transistor which has an end and gate connected to the ground and the other end connected to a third node; and

a fifth second-conductivity type transistor having an end connected to the second voltage supply and the other end and gate connected to the third node,

wherein the gates of the third and fourth second-conductivity type transistors are connected to the third node.

8. The level shifter of claim 7, further comprising:

a sixth second-conductivity type transistor connected between the first node and the gate of the second second-conductivity type transistor; and

a seventh second-conductivity type transistor connected between the second node and the gate of the first second-conductivity type transistor,

wherein when the potential of one of the first and second nodes changes from the ground potential to the potential of the second voltage supply, the sixth and seventh second-conductivity type transistors connect the one of the first and second nodes with the gate of the first or second second-conductivity type transistor to which the one of the first and second nodes is connected.

9. The level shifter of claim 8, wherein the gates of the sixth and seventh second-conductivity type transistors are connected to the first and second nodes, respectively, through a delay circuit.

13. The level shifter of claim 7, wherein the third, fourth and fifth first-conductivity type transistors are set to have a same threshold voltage which is lower than those of the other transistors.

15. The level shifter of claim 7, further comprising:

a first first-conductivity type high voltage transistor provided between the third first-conductivity type transistor and the gate of the second second-conductivity type transistor;

a second first-conductivity type high voltage transistor provided between the fourth first-conductivity type transistor and the gate of the first second-conductivity type transistor; and

a third first-conductivity type high voltage transistor provided between the fifth first-conductivity type transistor and the third node,

wherein the third, fourth and fifth first-conductivity type transistors are formed by low voltage transistors, and

gates of the first, second and third first-conductivity type high voltage transistors are controlled such that a potential equal to or greater than a peak inverse voltage of the low voltage transistor is prevented from being input to the third, fourth and fifth first-conductivity type transistors.

17. The level shifter of claim 15, wherein:

the gate of the first first-conductivity type high voltage transistor is connected to a gate of the third first-conductivity type transistor;

the gate of the second first-conductivity type high voltage transistor is connected to a gate of the fourth first-conductivity type transistor; and

the gate of the third first-conductivity type high voltage transistor is connected to the ground.

19. The level shifter of claim 7, wherein the current conversion circuit outputs a current equivalent to or greater than an OFF leakage current generated when the third and fourth first-conductivity type transistors are OFF.

29. The level shifter of claim 7, further comprising a resistor between the third node and the ground.

32. The level shifter of claim 7, further comprising a disconnection circuit, wherein

when the first voltage supply is shut down, the disconnection circuit disconnects the OFF leakage generation circuit from the current conversion circuit while stopping a level shift function.

35. A level shift device, comprising a plurality of level shifters, each of which is the level shifter of claim 7,

wherein the OFF leakage generation circuit included in each of the level shifters and a second-conductivity type transistor for generating a bias potential of a current mirror are shared among the plurality of level shifters.

10. A level shifter, comprising:

first and second first-conductivity type transistors for signal input, the first and second first-conductivity type transistors respectively receiving at gates complementary first and second input signals generated using a first voltage supply as a power supply and having ends connected to a ground and the other ends connected to first and second nodes, respectively;

cross-coupled first and second second-conductivity type transistors having ends connected to a second voltage supply and the other ends connected to the first and second nodes, respectively; and

a current interrupter for interrupting a through current by disconnecting the second voltage supply from the first or second second-conductivity type transistor when the levels of the input signals change,

wherein the current interrupter includes a third second-conductivity type transistor provided between the second voltage supply and the first second-conductivity type transistor and a fourth second-conductivity type transistor provided between the second voltage supply and the second second-conductivity type transistor,

the level shifter further includes

a fifth second-conductivity type transistor connected between a connection point of the first and third second-conductivity type transistors and a connection point of the second and fourth second-conductivity type transistors,

an OFF leakage generation circuit formed by a third first-conductivity type transistor having an end and gate connected to the ground and the other end connected to the third node, and

a sixth second-conductivity type transistor having an end connected to the second voltage supply and the other end and gate connected to the third node, and

the gate of the fifth second-conductivity type transistor is connected to the third node.

23. The level shifter of claim 10, wherein the first, second and third first-conductivity type 5 transistors are set to have a same threshold voltage which is lower than those of the other transistors.

25. The level shifter of claim 10, further comprising:

a first first-conductivity type high voltage transistor provided between the first first-conductivity type transistor and the first node;

a second first-conductivity type high voltage transistor provided between the second first-conductivity type transistor and the second node; and

a third first-conductivity type high voltage transistor provided between the third first-conductivity type transistor and the third node,

wherein the first, second and third first-conductivity type transistors are formed by low voltage transistors, and

gates of the first, second and third first-conductivity type high voltage transistors are controlled such that a potential equal to or greater than a peak inverse voltage of the low voltage transistor is prevented from being input to the first, second and third first-conductivity type transistors.

27. The level shifter of claim 10, wherein the current conversion circuit outputs a current equivalent to or greater than an OFF leakage current generated when the first and second first-conductivity type transistors are OFF.

30. The level shifter of claim 10, further comprising a resistor between the third node and the ground.

33. The level shifter of claim 10, further comprising a disconnection circuit, wherein

when the first voltage supply is shut down, the disconnection circuit disconnects the OFF leakage generation circuit from the current conversion circuit while stopping a level shift function.

36. A level shift device, comprising a plurality of level shifters, each of which is the level shifter of claim 10,

wherein the OFF leakage generation circuit included in each of the level shifters and a second-conductivity type transistor for generating a bias potential of a current mirror are shared among the plurality of level shifters.

11. A level shifter, comprising:

first and second first-conductivity type transistors for signal input, the first and second first-conductivity type transistors respectively receiving at gates complementary first and second input signals generated using a first voltage supply as a power supply and having ends connected to a ground and the other ends connected to first and second nodes, respectively;

a power supply circuit having an end connected to a second voltage supply and the other end connected to the first and second nodes, the power supply circuit supplying a voltage of the second voltage supply to one of the first and second nodes while interrupting the supply of the voltage of the second voltage supply to the other node;

a flip flop circuit for receiving potentials of the first and second nodes as inputs;

a disconnection circuit inserted between the first and second first-conductivity type transistors and the ground for disconnecting the first and second first-conductivity type transistors from the ground;

an OFF leakage generation circuit formed by a third first-conductivity type transistor having an end and gate connected to the ground and the other end connected to the third node;

a first second-conductivity type transistor connected between the first node and the second node; and

a second second-conductivity type transistor having an end connected to a second voltage supply and the other end and gate connected to the third node,

wherein the gate of the first second-conductivity type transistor is connected to the third node.

24. The level shifter of claim 11, wherein the first, second and third first-conductivity type transistors are set to have a same threshold voltage which is lower than those of the other transistors.

26. The level shifter of claim 11, further comprising:

a first first-conductivity type high voltage transistor provided between the first first-conductivity type transistor and the first node;

a second first-conductivity type high voltage transistor provided between the second first-conductivity type transistor and the second node; and

a third first-conductivity type high voltage transistor provided between the third first-conductivity type transistor and the third node,

wherein the first, second and third first-conductivity type transistors are formed by low voltage transistors, and

gates of the first, second and third first-conductivity type high voltage transistors are controlled such that a potential equal to or greater than a peak inverse voltage of the low voltage transistor is prevented from being input to the first, second and third first-conductivity type transistors.

28. The level shifter of claim 11, wherein the current conversion circuit outputs a current equivalent to or greater than an OFF leakage current generated when the first and second first-conductivity type transistors are OFF.

31. The level shifter of claim 11, further comprising a resistor between the third node and the ground.

34. The level shifter of claim 11, further comprising a disconnection circuit, wherein

when the first voltage supply is shut down, the disconnection circuit disconnects the OFF leakage generation circuit from the current conversion circuit while stopping a level shift function.

37. A level shift device, comprising a plurality of level shifters, each of which is the level shifter of claim 11,

wherein the OFF leakage generation circuit included in each of the level shifters and a second-conductivity type transistor for generating a bias potential of a current mirror are shared among the plurality of level shifters.