Low power sense amplifier for static random access memory
A low power sense amplifier for an SRAM is described. A first pass gate transistor is driven by bit line true and a second pass gate transistor is driven by bit line complement. A first pull down transistor driven by the bit line complement is coupled to the first pass gate transistor, and a second pull down transistor driven by the bit line true is coupled to the second pass gate transistor. A data line true is coupled to a node coupling the first pass gate transistor with the first pull down transistor and a data line complement is coupled to a node coupling the second pass gate transistor with the second pull down transistor. A current cut-off device cuts off parasitic current from flowing through the first pass gate transistor and the first pull down transistor and through the second pass gate transistor and the second pull down transistor.
1. A circuit, comprising:
a first pass gate transistor driven by a signal derived from a bit line true associated with a static random access memory (SRAM) cell;
a second pass gate transistor driven by a signal derived from a bit line complement associated with the SRAM cell;
a first pull down transistor driven by the signal derived from the bit line complement and coupled to the first pass gate transistor;
a second pull down transistor driven by the signal derived from the bit line true and coupled to the second pass gate transistor;
a data line true coupled to a node coupling the first pass gate transistor with the first pull down transistor, wherein the data line true is isolated from the bit line true by the first pass gate transistor;
a data line complement coupled to a node coupling the second pass gate transistor with the second pull down transistor, wherein the data line complement is isolated from the bit line complement by the second pass gate transistor; and
a current cut-off device that cuts off parasitic current from flowing through one of a first path formed from the first pass gate transistor and the first pull down transistor and a second path formed from the second pass gate transistor and the second pull down transistor.
2. The circuit according to claim 1 , wherein the current cut-off device includes a bit line complement pull down transistor that is configured to pull down the signal derived from the bit line complement towards ground and a bit line true pull down transistor that is configured to pull down the signal derived from the bit line true towards ground.
3. The circuit according to claim 2 , wherein an inverted data line complement drives the bit line complement pull down transistor and an inverted data line true drives the bit line true pull down transistor.
4. The circuit according to claim 1 , further including a data line true inverter that inverts the data line true.
5. The circuit according to claim 4 , further including a data line complement inverter that inverts the data line complement.
6. The circuit according to claim 5 , further including a differential to single ended signal converter that receives data from the data line true inverter and the data line complement inverter as input and generates a single output therefrom.
7. The circuit according to claim 1 , wherein the current cut-off device includes a first pass gate current cut-off transistor in series with the first pass gate transistor and a second pass gate current cut-off transistor in series with the second pass gate transistor, the first pass gate current cut-off transistor is configured to cut off current generated from a supply voltage to the first pass gate transistor and the second pass gate current cut-off transistor is configured to cut off current generated from the supply voltage to the second pass gate transistor.
8. The circuit according to claim 7 , wherein an inverted data line true drives the first pass gate current cut-off transistor and an inverted data line complement drives the second pass gate current cut-off transistor.
9. The circuit according to claim 1 , further comprising an isolation device configured to receive the signal derived from the bit line true and the signal derived from the bit line complement from the SRAM cell.
10. The circuit according to claim 9 , wherein the isolation device includes a first pass transistor that passes the signal derived from the bit line true therethrough to drive the first pass gate transistor and a second pass transistor that passes the signal derived from the bit line complement therethrough to drive the second pass gate transistor, the first pass gate transistor and the second pass gate transistor operating in conjunction to reduce power on bit line true and bit line complement.
11. A sense amplifier for a static random access memory (SRAM) cell, comprising:
a first pass transistor configured to pass data that is on a signal derived from a bit line true associated with the SRAM cell;
a second pass transistor configured to pass data that is on a signal derived from a bit line complement associated with the SRAM cell;
a first pass gate transistor configured to be driven by the data that is on the signal derived from the bit line true passing through the first pass transistor;
a second pass gate transistor configured to be driven by the data that is on the signal derived from the bit line complement passing through the second pass transistor;
a first pull down transistor driven by the data that is on the signal derived from the bit line complement and coupled to the first pass gate transistor;
a second pull down transistor driven by the data that is on the signal derived from the bit line true and coupled to the second pass gate transistor;
a data line true coupled to a node coupling the first pass gate transistor with first pull down transistor, wherein the data line true is isolated from the bit line true by the first pass gate transistor;
a data line complement coupled to a node coupling the second pass gate transistor with the second pull down transistor, wherein the data line complement is isolated from the bit line complement by the second pass gate transistor; and
a current cut-off device configured to cut off parasitic current from flowing through one of a first path formed from the first pass gate transistor and the first pull down transistor and a second path formed from the second pass gate transistor and the second pull down transistor during an amplification state.
12. The sense amplifier according to claim 11 , wherein the current cut-off device includes a bit line complement pull down transistor that is configured to pull down the signal derived from the bit line complement towards ground and a bit line true pull down transistor that is configured to pull down the signal derived from the bit line true towards ground.
13. The sense amplifier according to claim 12 , wherein an inverted data line complement drives the bit line complement pull down transistor and an inverted data line true drives the bit line true pull down transistor.
14. The sense amplifier according to claim 11 , further including a data line true inverter that inverts the data line true.
15. The sense amplifier according to claim 14 , further including a data line complement inverter that inverts the data line complement.
16. The sense amplifier according to claim 15 , further including a differential to single ended signal converter that receives data from the data line true inverter and the data line complement inverter as input and generates a single output therefrom.
17. The sense amplifier according to claim 11 , wherein the current cut-off device includes a first pass gate current cut-off transistor in series with the first pass gate transistor and a second pass gate current cut-off transistor in series with the second pass gate transistor, the first pass gate current cut-off transistor is configured to cut off current generated from a supply voltage to the first pass gate transistor and the second pass gate current cut-off transistor is configured to cut off current generated from the supply voltage to the second pass gate transistor.
18. The sense amplifier according to claim 17 , wherein an inverted data line true drives the first pass gate current cut-off transistor and an inverted data line complement drives the second pass gate current cut-off transistor.