Method and apparatus for integrated level-shifter and memory clock

• US 10,706,916 B1
• Filed: 04/03/2019
• Issued: 07/07/2020
• Est. Priority Date: 04/03/2019
• Status: Active Grant

• Current Assignee: Synopsys Incorporated
• Original Assignee: Synopsys Incorporated
• Inventors: Pilo, Harold, Barth, Jr., John Edward
• Primary Examiner(s): Tran, Michael T
• Application Number:
  US16/374,666
• Time in Patent Office: 461 Days
• Field of Search: 36518911, 365205
• CPC Class Codes: G11C 11/417 for memory cells of the field-effect type
• CPC Class Codes: G11C 7/225 Clock input buffers

Abstract

An integrated level-shifter and memory clock is disclosed that minimizes delay of voltage level-shifting from an external clock on a first logic supply voltage to an internal clock on a higher array supply voltage that is pulse-width independent of the external clock used to generate the internal clock. The generation of the internal clock on the higher array supply voltages is accomplished in two stages of logic. An array-tracking timing delay circuit mimics access delay to generate a MRST_P to reset the internal clock on the higher array supply voltage.

Claims

1. A level-shifting circuit configured to provide a CLKI signal in a high voltage domain in response to a CLK signal in a low voltage domain, comprising:

a first NFET having a gate coupled to the CLK signal in the low voltage domain, a drain coupled to a NCLK_N node, and a source coupled to a first intermediate node;

a second NFET having a drain coupled to the first intermediate node, a source coupled to ground, and a gate coupled to an ENCLK_T node;

a first PFET having a gate coupled to the CLK signal, a drain coupled to the NCLK_N node, and a source coupled to a second intermediate node;

a second PFET having a drain coupled to the second intermediate node, a source coupled to a high voltage source in the high voltage domain, and a gate coupled to the CLKI signal;

a third NFET having a drain coupled to the NCLK_N node, a source coupled to the first intermediate node, and a gate coupled to the CLKI signal;

a first inverter having an input coupled to the NCLK_N node and an output coupled to the CLKI signal;

a third PFET having a source coupled to the high voltage source in the high voltage domain, a gate coupled to the ENCLK_T node, and a drain coupled to the NCLK_N node;

a second inverter in a low power domain having an input coupled to the CLK signal and an output coupled to a third intermediate node;

a first nor gate having a first input coupled to the third intermediate node, a second input coupled to the ENCLK_T node, and an output coupled to a fourth intermediate node; and

a second nor gate having a first input coupled to the fourth intermediate node;

a second input coupled to a MRST_P input signal, and an output coupled to the ENCLK_T node.

2. The level-shifting circuit of claim 1, wherein the third NFET is configured as a half-latch to maintain the NCLK_N node at a discharged state.

3. The level-shifting circuit of claim 2, wherein the CLK signal includes a positive edge configured to discharge the NCLK_N node to activate the half-latch.

4. The level-shifting circuit of claim 3, wherein the NCLK_N node is coupled to the input of the first inverter and configured to generate the CLKI signal.

5. The level-shifting circuit of claim 4, wherein the CLK signal propagates through two gate delays to generate the CLKI signal.

6. The level-shifting circuit of claim 1 further comprising an array-tracking timing delay circuit configured to provide the MRST_P input signal to reset the level-shifting circuit.

7. The level-shifting circuit of claim 6, wherein the array-tracking timing delay circuit includes a plurality of inverters.

8. The level-shifting circuit of claim 6, wherein the CLK signal includes a first pulse-width and the CLKI signal includes a pulse-width that is independent of the first pulse-width from the CLK signal.

9. The level-shifting circuit of claim 8, wherein the MRST_P input signal determines the pulse-width of the CLKI signal.

10. A method of operating a memory clock level-shifter configured to generate a CLKI signal in a high voltage domain in response to a CLK signal in a low voltage domain comprising the steps:

configuring a first NFET having a gate coupled to the CLK signal in a low voltage domain, a drain coupled to a NCLK_N node, and a source coupled to a first intermediate node;

configuring a second NFET having a drain coupled to the first intermediate node, a source coupled to ground, and a gate coupled to an ENCLK_T node;

configuring a first PFET having a gate coupled to the CLK signal, a drain coupled to the NCLK_N node, and a source coupled to a second intermediate node;

configuring a second PFET having a drain coupled to the second intermediate node, a source coupled to a high voltage source in the high voltage domain, and a gate coupled to the CLKI signal;

configuring a third NFET having a drain coupled to the NCLK_N node, a source coupled to the first intermediate node, and a gate coupled to the CLKI signal;

configuring a first inverter having an input coupled to the NCLK_N node and an output coupled to the CLKI signal;

configuring a third PFET having a source coupled to the high voltage source in the high voltage domain, a gate coupled to the ENCLK_T node, and a drain coupled to the NCLK_N node;

configuring a second inverter having an input coupled to the CLK signal and an output coupled to a third intermediate node;

configuring a first nor gate having a first input coupled to the third intermediate node, a second input coupled to the ENCLK_T node, and an output coupled to a fourth intermediate node; and

configuring a second nor gate having a first input coupled to the fourth intermediate node;

a second input coupled to a MRST_P input signal, and an output coupled to the ENCLK_T node.

11. The method of operating the memory clock level-shifter of claim 10 further comprising the step of maintaining the NCLK_N node at a discharged state with a half-latch.

12. The method of operating the memory clock level-shifter of claim 11 further comprising the step of activating the half-latch with a positive edge of the CLK signal to discharge the NCLK_N node.

13. The method of operating the memory clock level-shifter of claim 12 wherein the NCLK_N node is coupled to the input of the first inverter and further comprises the step of inverting the input at the first inverter to generate the CLKI signal.

14. The method of operating the memory clock level-shifter of claim 13 further comprising the step of propagating the CLK signal through two gate delays to generate the CLKI signal.

15. The method of operating the memory clock level-shifter of claim 10 further comprising an array-tracking timing delay circuit and the step further comprises resetting the memory clock level-shifter with the MRST_P input signal from an output of the array-tracking timing delay circuit.

16. The method of operating the memory clock level-shifter of claim 15, wherein the array-tracking timing delay circuit further comprises the step of mimicking a dummy array bit-cell to generate the MRST_P input signal.

17. The method of operating the memory clock level-shifter of claim 15, wherein the CLK signal includes a first pulse-width and the step further comprises generating the CLKI signal that is pulse-width independent with the first pulse-width of the CLK signal.

18. The method of operating the memory clock level-shifter of claim 17 further comprising the step of controlling a pulse-width of the CLKI signal with the MRST_P input signal.