Granted Patent B2

US 8,410,839 · App. 13/041,065 · Granted Apr 2, 2013

Abstract

Claims (50)

1. A circuit comprising:

a pull-up transistor coupled to an output and operable to receive a control signal;

a pull-down transistor coupled to the pull-up transistor and the output and operable to receive the control signal;

a battery element coupled between either of 1) a high supply rail having a high supply voltage or a low supply rail having a low supply voltage and 2) the pull-up transistor or the pull-down transistor, respectively, wherein the battery element maintains a voltage substantially equal to the high supply voltage minus the low supply voltage and a target swing voltage.

2. The circuit of claim 1 , wherein the pull-up transistor is a p-type field effect transistor (PFET).

3. The circuit of claim 1 , wherein the pull-down transistor is an n-type field effect transistor (NFET).

4. The circuit of claim 1 , wherein the battery element is coupled to the low supply rail and the pull-down transistor.

5. The circuit of claim 4 , wherein the battery element comprises:

a transistor having an input and terminals, said terminals coupled to the low supply rail and the pull down transistor;

a bias network coupled to the input of the battery element transistor; and

a clamping transistor coupled to the high supply rail, the battery element transistor, and a clamping voltage.

6. The circuit of claim 5 wherein the clamping transistor has a threshold voltage and the clamping voltage is substantially equal to the high supply voltage minus the target swing voltage plus the threshold voltage.

7. The circuit of claim 5 wherein the bias network comprises:

an RC circuit;

a transistor coupled to the RC circuit;

a bias resistor coupled to the bias network transistor and the low supply rail; and

a voltage supply coupled to the high supply rail that maintains the swing voltage and coupled to the bias network transistor.

8. The circuit of claim 1 , wherein the battery element is coupled to the high supply rail and the pull-up transistor.

9. The circuit of claim 8 , wherein the battery element comprises:

a first transistor having an input and terminals, said terminals coupled to the high supply rail and the pull up transistor;

a bias network coupled to the input of the battery element transistor; and

a second transistor coupled to the low supply rail, the first transistor, and a clamping voltage.

10. The circuit of claim 9 wherein the first transistor has a threshold voltage and the clamping voltage is substantially equal to the low supply voltage plus the target swing voltage minus the threshold voltage.

11. The circuit of claim 9 wherein the bias network comprises:

an RC circuit;

a transistor coupled to the RC circuit;

a bias resistor coupled to the bias network transistor and the low supply rail; and

a voltage supply coupled to the high supply rail that maintains the swing voltage and coupled to the bias network transistor.

12. The circuit of claim 1 wherein a gate of the pull-up transistor is coupled to a gate of the pull-down transistor.

13. A method for generating a signal comprising:

pulling up an output to a high supply rail having a high supply voltage when an input signal is high;

pulling down the output to a positive terminal of a battery element when the input signal is low, the positive terminal having a voltage substantially equal to a battery voltage plus a low supply voltage; and

maintaining the battery voltage across the battery element at a value that is substantially equal to the high supply voltage minus 1) the low supply voltage and 2) a target swing voltage.

14. The method of claim 13 , wherein maintaining the battery voltage comprises:

biasing a battery transistor to maintain a voltage equal to a sum of 1) the target swing voltage and 2) a difference between the high supply voltage and the low supply voltage; and

clamping a positive terminal of the battery element to a voltage substantially equal to the high supply voltage minus the target swing voltage when the input signal goes low.

15. A method for generating a signal comprising:

pulling down an output to a low supply rail having a low supply voltage when an input signal is low;

pulling up the output to a negative terminal of a battery element when the input signal is low, the negative terminal having a voltage substantially equal to a high supply voltage minus a battery voltage; and

maintaining the battery voltage across the battery element substantially equal to the high supply voltage minus the low supply voltage and a target swing voltage.

16. The method of claim 15 , wherein maintaining the battery voltage comprises:

biasing a transistor to maintain a voltage equal to a sum of 1) the target swing voltage and 2) the difference between the high supply voltage and the low supply voltage; and

clamping the negative terminal of the battery element to a voltage substantially equal the low supply voltage plus the target swing voltage to when the input signal goes high.

17. A circuit comprising:

a pull-up transistor coupled to an output and operable to receive a control signal;

a pull-down transistor coupled to the pull-up transistor and the output and operable to receive the control signal; and

means for maintaining a voltage substantially equal to the high supply voltage minus the low supply voltage and a target swing voltage.

18. The circuit of claim 17 , wherein the pull-up transistor is a p-type field effect transistor (PFET).

19. The circuit of claim 17 , wherein the pull-down transistor is an n-type field effect transistor (NFET).

20. The circuit of claim 17 wherein a gate of the pull-up transistor is coupled to a gate of the pull-down transistor.

Assignments (9)