SRAM with read and write assist
View Patent ↗A memory includes an SRAM bitcell including a pair of cross-coupled inverters, wherein a first inverter of the pair includes a first device having a body and a second inverter of the pair includes a second device having a body. A first selection circuit has a first input coupled to a first supply voltage terminal, a second input coupled to a second supply voltage terminal, and an output coupled to a first current electrode of the first device and to a first current electrode of the second device. A second selection circuit has a first input coupled to the first supply voltage terminal, a second input coupled to the second supply voltage terminal, and an output coupled to the body of each of the first and second devices. A word line coupled to the SRAM bitcell is driven by a word line driver coupled to the first supply voltage terminal.
1. A memory comprising:
a static random access memory (SRAM) bitcell comprising a pair of cross-coupled inverters, wherein a first inverter of the pair of cross-coupled inverters includes a first device having a body and a second inverter of the pair of cross-coupled inverters includes a second device having a body;
a first selection circuit having a first input coupled to a first supply voltage terminal, a second input coupled to a second supply voltage terminal, and an output coupled to a first current electrode of the first device and to a first current electrode of the second device;
a second selection circuit having a first input coupled to the first supply voltage terminal, a second input coupled to the second supply voltage terminal, and an output coupled to the body of the first device and to the body of the second device;
a word line coupled to the SRAM bitcell; and
a word line driver coupled to the first supply voltage terminal and which drives the word line.
2. The memory of claim 1 , wherein a voltage of the second supply voltage terminal is less than a voltage of the first supply voltage terminal.
3. The memory of claim 2 , wherein, during a read operation of the SRAM bitcell, the first selection circuit couples the first supply voltage terminal to the first current electrode of the first device and to the first current electrode of the second device and the second selection circuit couples the second supply voltage terminal to the body of the first device and the body of the second device.
4. The memory of claim 3 , wherein, during a write operation of the SRAM bitcell, the first selection circuit couples the second supply voltage terminal to the first current electrode of the first device and to the first current electrode of the second device and the second selection circuit couples the second supply voltage terminal to the body of the first device and the body of the second device.
5. The memory of claim 4 , wherein, during a standby mode of the SRAM bitcell, the first selection circuit couples the second supply voltage terminal to the first current electrode of the first device and to the first current electrode of the second device and the second selection circuit couples the first supply voltage terminal to the body of the first device and the body of the second device.
6. The memory of claim 3 , wherein, during a write operation of the SRAM bitcell, the first selection circuit couples the second supply voltage terminal to the first current electrode of the first device and to the first current electrode of the second device and the second selection circuit couples the first supply voltage terminal to the body of the first device and the body of the second device.
7. The memory of claim 1 , wherein, during a write operation of the SRAM bitcell, the first selection circuit couples the second supply voltage terminal to the first current electrode of the first device and to the first current electrode of the second device and the second selection circuit couples the second supply voltage terminal to the body of the first device and the body of the second device.
8. The memory of claim 1 , wherein, during a write operation of the SRAM bitcell, the first selection circuit couples the second supply voltage terminal to the first current electrode of the first device and to the first current electrode of the second device and the second selection circuit couples the first supply voltage terminal to the body of the first device and the body of the second device.
9. The memory of claim 1 , further comprising a reduced voltage generator coupled to the first supply voltage terminal and providing the second supply voltage terminal, wherein a voltage level of the second supply voltage terminal is generated from a voltage level of the first voltage supply terminal.
10. The memory of claim 9 , wherein, during a standby mode of the SRAM bit cell, the reduced voltage generator is disabled.
11. A method for operating an SRAM bitcell having a first P channel device and a second P channel device, the first P channel device having a body and the second P channel device having a body, the method comprising:
during a read operation of the SRAM bitcell, providing a first supply voltage to a first current electrode of the first P channel device and a first current electrode of the second P channel device, and providing a second supply voltage to the body of the first P channel device and the body of the second P channel device;
during a write operation of the SRAM bitcell, providing the second supply voltage to the first current electrode of the first P channel device and the first current electrode of the second P channel device, and providing one of the first supply voltage or the second supply voltage to the body of the first P channel device and the body of the second P channel device; and
during the read operation and during the write operation, driving a word line coupled to the SRAM bitcell using one of the first supply voltage or the second supply voltage.
12. The method of claim 11 , wherein the second supply voltage is less than the first supply voltage.
13. The method of claim 11 , further comprising:
generating the second supply voltage from the first supply voltage.
14. The method of claim 11 , further comprising:
during a standby mode of the SRAM bitcell, providing the second supply voltage to the first current electrode of the first P channel device and the first current electrode of the second P channel device, and providing the first supply voltage to the body of the first P channel device and the body of the second P channel device.
15. The method of claim 14 , wherein, during the write operation of the SRAM bitcell, the providing the one of the first supply voltage or the second supply voltage to the body of the first P channel device and the body of the second P channel device comprises providing the second supply voltage to the body of the first P channel device and the body of the second P channel device.
16. The method of claim 11 , wherein, during the read operation and during the write operation, the driving the word line coupled to the SRAM bitcell using one of the first supply voltage or the second supply voltage comprises driving the word line using the first supply voltage.
17. A memory coupled to a first supply voltage terminal and to a second supply voltage terminal, comprising:
a static random access memory (SRAM) bitcell comprising a first P channel device having a body and a second P channel device having a body, and wherein a voltage of the second supply voltage terminal is less than a voltage of the first supply voltage terminal;
a word line coupled to the SRAM bitcell;
a word line driver coupled to the first supply voltage terminal and which drives the word line;
a first multiplexer having a first input coupled to a first supply voltage terminal, a second input coupled to a second supply voltage terminal, and an output coupled to a first current electrode of the first P channel device and to a first current electrode of the second P channel device;
a second multiplexer having a first input coupled to the first supply voltage terminal, a second input coupled to the second supply voltage terminal, and an output coupled to the body of the first P channel device and to the body of the second P channel device, wherein:
during a read operation of the SRAM bitcell, the first multiplexer couples the first supply voltage terminal to the first current electrode of the first P channel device and to the first current electrode of the second P channel device and the second multiplexer couples the second supply voltage terminal to the body of the first P channel device and the body of the second P channel device, and
during a write operation of the SRAM bitcell, the first multiplexer couples the second supply voltage terminal to the first current electrode of the first P channel device and to the first current electrode of the second P channel device and the second multiplexer couples one of the first supply voltage terminal or the second supply voltage terminal to the body of the first P channel device and the body of the second P channel device.
18. The memory of claim 17 , wherein, during a standby mode of the SRAM bitcell, the first multiplexer couples the second supply voltage terminal to the first current electrode of the first P channel device and to the first current electrode of the second P channel device and the second multiplexer couples the first supply voltage terminal to the body of the first P channel device and the body of the second P channel device.
19. The memory of claim 17 , further comprising a reduced voltage generator coupled to the first supply voltage terminal and providing the second supply voltage terminal, wherein a voltage level of the second voltage supply terminal is generated from a voltage level of the first voltage supply terminal.
20. The memory of claim 19 , wherein, during a standby mode of the SRAM bit cell, the reduced voltage generator is disabled.