Memory with low power mode for WRITE
The present invention describes circuitry and a method of providing a low power WRITE mode of operation for an integrated circuit comprising an SRAM memory to provide a reduced IDDQ relative to the IDDQ of a full active mode. In one aspect, the circuitry includes an SRAM memory array, mode control circuitry coupled to the array and configured to alter a supply voltage level to the SRAM array based on a mode of operation. The circuitry also includes control inputs coupled to the mode control circuitry for selecting one of the low power write mode, the full active mode, and optionally a retention mode of operation. The mode control circuitry is configured to receive the control inputs to select one of the three modes of operation, and to alter one or more supply voltage levels to the array, for example, the Vss supply voltage using a Vss supply circuit and the Vdd supply voltage using a Vdd supply circuit, based on the selected mode of operation. The mode control circuitry may also comprise a bitline precharge circuit configured to alter a bitline precharge voltage.
1. An integrated circuit comprising a memory configured to provide a low power WRITE mode of operation having a reduced IDDQ relative to the IDDQ of a full active mode, the integrated circuit comprising:
an SRAM memory array;
mode control circuitry coupled to the array and configured to alter one or more supply voltage levels to the SRAM array based on a mode of operation; and
control inputs coupled to the mode control circuitry for selecting one of the low power write mode, and the full active mode of operation;
wherein the mode control circuitry is configured to receive the control inputs in order to select the one of the low power WRITE mode, and the full active mode of operation based on the control inputs, and to alter the one or more supply voltage levels for the SRAM array based on the selected mode of operation; and
wherein the mode control circuitry for the SRAM memory array comprises a cycle timing circuit configured to regulate the timing of the modes of operation.
2. The integrated circuit of claim 1 , wherein the mode control circuitry comprises a Vss supply circuit coupled between an array Vss terminal and a Vss supply voltage, wherein the Vss supply circuit is configured to raise a Vss-array voltage at the array Vss terminal above the Vss supply voltage level in response to the selected mode.
3. The integrated circuit of claim 1 , wherein the mode control circuitry is configured to perform a WRITE operation in the low power write mode and in the full active mode of operation.
4. The integrated circuit of claim 1 , wherein the mode control circuitry is configured to perform a READ operation in the full active mode of operation.
5. The integrated circuit of claim 4 , wherein the mode control circuitry is configured to initiate a READ while in the low power write mode.
6. The integrated circuit of claim 1 wherein the mode control circuitry is further configured to select a retention mode and perform a memory retention operation using the selected retention mode.
7. The integrated circuit of claim 6 , wherein the supply voltage levels used in the retention mode are about the same as in the low power write mode.
8. The integrated circuit of claim 6 , wherein the supply voltage levels used in the write mode are intermediate between the voltage levels used in the retention mode and in the full active mode.
9. The integrated circuit of claim 1 , wherein during the cycle timing of the cycle timing circuit there is no latency in the transition time between the low power write mode and the full active mode.
10. The integrated circuit of claim 2 , further comprising a write driver circuit, said write driver operable to drive a bit line toward the VSS supply voltage.
11. The integrated circuit of claim 2 , further comprising a wordline driver circuit configured to reduce the wordline voltage to a lower voltage in the low power write mode than in the full active mode.
12. The integrated circuit of claim 2 , wherein the mode control circuitry comprises a Vdd supply circuit coupled between an array Vdd terminal and a Vdd supply voltage, wherein the Vdd supply circuit is configured to reduce a Vdd-array voltage at the array Vdd terminal below the Vdd supply voltage level in response to the selected mode.
13. The integrated circuit of claim 1 wherein the mode control circuitry comprises a bitline precharge circuit coupled to one or more bitlines of the array, the bitline precharge circuit configured to precharge said one or more bitlines to a lower voltage in the low power write mode than in the full active mode.
14. An integrated circuit comprising a memory configured to provide a low power WRITE mode of operation having a reduced IDDQ relative to the IDDQ of a full active mode, the integrated circuit comprising:
an SRAM memory array;
mode control circuitry coupled to the array and configured to alter one or more supply voltage levels to the SRAM array based on a mode of operation; and
control inputs coupled to the mode control circuitry for selecting of the low power write mode, and the full active mode of operation;
wherein the mode control circuitry is configured to receive the control inputs in order to select the one of the low power WRITE mode, and the full active mode of operation based on the control inputs, and to alter the one or more supply voltage levels for the SRAM array based on the selected mode of operation;
wherein the mode control circuitry comprises a Vss supply circuit coupled between an array Vss terminal and a Vss supply voltage, wherein the Vss supply circuit is configured to raise a Vss-array voltage at the array Vss terminal above the Vss supply voltage level in response to the selected mode; and
wherein the mode control circuitry is configured to initiate a READ operation and to concurrently reduce the Vss-array voltage to the Vss supply voltage level during a mode change from the low power WRITE mode to the full active mode.
15. An integrated circuit comprising a memory configured to provide a low power WRITE mode of operation having a reduced IDDQ relative to the IDDQ of a full active mode, the integrated circuit comprising:
an SRAM memory array;
mode control circuitry coupled to the array and configured to alter one or more supply voltage levels to the SRAM array based on a mode of operation; and
control inputs coupled to the mode control circuitry for selecting one of the low power write mode, and the full active mode of operation;
wherein the mode control circuitry is configured to receive the control inputs in order to select the one of the low power WRITE mode, and the full active mode of operation based on the control inputs, and to alter the one or more supply voltage levels for the SRAM array based on the selected mode of operation;
wherein the mode control circuitry is further configured to select a retention mode and perform a memory retention operation using the selected retention mode; and
wherein the mode control circuitry is configured to raise the Vss-array voltage at the array Vss terminal above the Vss supply voltage level in the retention mode and in the low power WRITE mode.
16. The integrated circuit of claim 2 , further comprising a wordline driver circuit configured to reduce the wordline voltage by about one diode voltage drop lower in the low power write mode than in the full active mode.
17. The integrated circuit of claim 2 , wherein the mode control circuitry comprises a Vdd supply circuit coupled between an array Vdd terminal and a Vdd supply voltage, wherein the Vdd supply circuit is configured to reduce a Vdd-array voltage at the array Vdd terminal by about one diode voltage drop below the Vdd supply voltage level in response to the selected mode.
18. The integrated circuit of claim 2 , wherein the Vss supply circuit is configured to raise the Vss-array voltage at the array Vss terminal by about one diode voltage drop above the Vss supply voltage level in response to the selected mode.