Memory having a latching sense amplifier resistant to negative bias temperature instability and method therefor
View Patent ↗An integrated circuit includes a memory cell and a sense amplifier coupled to the memory cell via a first bit line and a second bit line. The sense amplifier includes first and second inverters cross-coupled to provide a latch. The first inverter is responsive to a first data signal provided by the memory cell over the first bit line. The second inverter is responsive to a second data signal as provided by the memory cell over the second bit line. A first negative bias temperature instability (NBTI) compensation transistor includes a source electrode coupled to receive a reference voltage, a drain electrode coupled to a source electrode of the first inverter, and a gate electrode coupled to first logic responsive to the first data signal. A second NBTI compensation transistor includes a source electrode coupled to receive the reference voltage, a drain electrode coupled to a source electrode of the second inverter, and a gate electrode coupled to second logic responsive to the second data signal, wherein the second data signal is a logical complement of the first data signal.
1. An integrated circuit comprising:
a memory cell; and
a sense amplifier coupled to the memory cell via a first and second bit line, comprising:
a first inverter responsive to a first data signal provided by the memory cell over the first bit line,
a second inverter responsive to a second data signal provided by the memory cell over the second bit line, wherein the second inverter is cross-coupled to the first inverter,
a first negative bias temperature instability (NBTI) compensation transistor comprising a source electrode coupled to a reference voltage, a drain electrode coupled to a source electrode of the first inverter, and a gate electrode coupled to first logic responsive to one of the first or second data signals,
a second NBTI compensation transistor comprising a source electrode coupled to the reference voltage, a drain electrode coupled to a source electrode of the second inverter, and a gate electrode coupled to second logic responsive to one of the first or second data signals, wherein the second data signal is a logical complement of the first data signal, and
an equilibrium transistor comprising a first source/drain electrode coupled to the drain electrode of the first NBTI compensation transistor and the source electrode of the first inverter, a second source/drain electrode coupled to the drain electrode of the second NBTI compensation transistor and the source electrode of the second inverter, and a gate electrode coupled to receive an enable signal.
2. The integrated circuit of claim 1 wherein the equilibrium transistor is on during a hold mode of the sense amplifier.
3. The integrated circuit of claim 1 wherein the equilibrium transistor is off during a sense mode of the sense amplifier.
4. The integrated circuit of claim 1 wherein the first NBTI compensation transistor and the second NBTI compensation transistor are p-channel transistors.
5. The integrated circuit of claim 1 wherein the memory cell is a one-time programmable memory cell.
6. The integrated circuit of claim 1 wherein the memory cell is one of a plurality of memory cells coupled to the first and second bit lines.
7. An integrated circuit comprising:
a memory cell; and
a sense amplifier coupled to the memory cell via a first and second bit line, comprising:
a first inverter responsive to a first data signal provided by the memory cell over the first bit line,
a second inverter responsive to a second data signal provided by the memory cell over the second bit line, wherein the second inverter is cross-coupled to the first inverter,
a first negative bias temperature instability (NBTI) compensation transistor comprising a source electrode coupled to a reference voltage, a drain electrode coupled to a source electrode of the first inverter, and a gate electrode coupled to first logic responsive to one of the first or second data signals,
a second NBTI compensation transistor comprising a source electrode coupled to the reference voltage, a drain electrode coupled to a source electrode of the second inverter, and a gate electrode coupled to second logic responsive to one of the first or second data signals, wherein the second data signal is a logical complement of the first data signal, and
a supply voltage bias circuit comprising
a first supply voltage bias transistor comprising a source electrode coupled to a supply voltage of the sense amplifier, a drain electrode coupled to the source electrode of the first NBTI transistor and the source electrode of the second NBTI transistor, and a gate electrode coupled to receive an enable signal, and
a second supply voltage bias transistor comprising a source electrode coupled to the supply voltage of the sense amplifier, a drain electrode coupled to the source electrode of the first NBTI transistor and the source electrode of the second NBTI transistor, and a gate electrode coupled to the drain electrode of the first and second source voltage bias transistors.
8. A sense amplifier circuit comprising:
a first inverter comprising a first transistor and a second transistor, wherein
the first transistor comprises a source electrode, a drain electrode coupled to a first data node, and a gate electrode coupled to a second data node, and
the second transistor comprises a drain electrode coupled to the first data node, a source electrode, and a gate electrode coupled to the gate electrode of the first transistor;
a second inverter comprising a third transistor and a fourth transistor, wherein
the third transistor comprises a source electrode coupled to the source electrode of the first transistor, a drain electrode coupled to the second data node, and a gate electrode coupled to the first data node, and
a fourth transistor comprises a drain electrode coupled to the second data node, a source electrode coupled to the source electrode of the second transistor, and a gate electrode coupled to the gate electrode of the third transistor;
a first negative bias temperature instability (NBTI) compensation transistor comprising a source electrode coupled to a reference voltage, a drain electrode coupled to the source electrode of the first transistor, and a gate electrode;
a second NBTI compensation transistor comprising a source electrode coupled to the reference voltage, a drain electrode coupled to the source electrode of the third transistor and the drain electrode of the first NBTI compensation transistor, and a gate electrode;
a first logic comprising an input coupled to the first data node and an output coupled to the gate electrode of the first NBTI compensation transistor, wherein the first logic is responsive to a first signal provided by the first data node and an enable signal;
a second logic comprising an input coupled to the second data node and an output coupled to the gate electrode of the second NBTI compensation transistor, wherein the second logic is responsive to a second signal provided by the second data node and the enable signal; and
a supply voltage bias circuit coupled between the first and second NBTI transistors and a supply voltage of the sense amplifier, wherein the supply voltage bias circuit includes
a first supply voltage bias transistor comprising a source electrode coupled to the supply voltage of the sense amplifier, a drain electrode coupled to the source electrode of the first NBTI transistor and the source electrode of the second NBTI transistor, and a gate electrode coupled to receive an enable signal, and
a second supply voltage bias transistor comprising a source electrode coupled to the supply voltage of the sense amplifier, a drain electrode coupled to the source electrode of the first NBTI transistor and the source electrode of the second NBTI transistor, and a gate electrode coupled to the drain electrode of the first and second source voltage bias transistors.
9. The sense amplifier circuit of claim 8 further comprising:
the first logic is configured to couple the first data node to the gate of the first NBTI compensation transistor in response to a logic high enable signal, and
the first logic is configured to couple the gate of the first NBTI compensation transistor to ground potential in response to a logic low enable signal; and
the second logic is configured to couple the second data node to the gate of the second NBTI compensation transistor in response to the logic high enable signal, and
the second logic is configured to couple the gate of the first NBTI compensation transistor to ground potential in response to the logic low enable signal.
10. The sense amplifier circuit of claim 8 wherein the second data signal is a logical complement to the first data signal.
11. The sense amplifier circuit of claim 8 wherein the first and second NBTI compensation transistors are p-channel transistors.
12. The sense amplifier circuit of claim 11 wherein the first transistor and the third transistor are p-channel transistors.
13. The sense amplifier circuit of claim 8 further comprising:
a first bit line coupled to a memory cell;
a second bit line coupled to the memory cell, wherein
the first signal is responsive to a data signal provided by the memory cell over the first bit line, and
the second signal is responsive to a logical complement of the data signal provided by the memory cell over the second bit line.
14. The sense amplifier circuit of claim 13 wherein the memory cell is a one-time programmable memory cell.
15. The sense amplifier circuit of claim 13 wherein the memory cell is one of a plurality of memory cells coupled to the first and second bit lines.
16. A sense amplifier circuit comprising:
a first inverter comprising a first transistor and a second transistor, wherein
the first transistor comprises a source electrode, a drain electrode coupled to a first data node, and a gate electrode coupled to a second data node, and
the second transistor comprises a drain electrode coupled to the first data node, a source electrode, and a gate electrode coupled to the gate electrode of the first transistor;
a second inverter comprising a third transistor and a fourth transistor, wherein
the third transistor comprises a source electrode coupled to the source electrode of the first transistor, a drain electrode coupled to the second data node, and a gate electrode coupled to the first data node, and
a fourth transistor comprises a drain electrode coupled to the second data node, a source electrode coupled to the source electrode of the second transistor, and a gate electrode coupled to the gate electrode of the third transistor;
a first negative bias temperature instability (NBTI) compensation transistor comprising a source electrode coupled to a reference voltage, a drain electrode coupled to the source electrode of the first transistor, and a gate electrode;
a second NBTI compensation transistor comprising a source electrode coupled to the reference voltage, a drain electrode coupled to the source electrode of the third transistor and the drain electrode of the first NBTI compensation transistor, and a gate electrode;
a first logic comprising an input coupled to the first data node and an output coupled to the gate electrode of the first NBTI compensation transistor, wherein the first logic is responsive to a first signal provided by the first data node and an enable signal;
a second logic comprising an input coupled to the second data node and an output coupled to the gate electrode of the second NBTI compensation transistor, wherein the second logic is responsive to a second signal provided by the second data node and the enable signal; and
an equilibrium transistor comprising:
a first source/drain electrode coupled to the drain electrode of the first NBTI compensation transistor and the source electrode of the first transistor,
a second source/drain electrode coupled to the drain electrode of the second NBTI compensation transistor and the source electrode of the third transistor, and
a gate electrode coupled to receive the logical complement of the enable signal, wherein the equilibrium transistor couples the drain electrode of the first NBTI compensation transistor and the source electrode of the first transistor to the drain electrode of the second NBTI compensation transistor and the source electrode of the third transistor.
17. A method for compensating for negative bias temperature instability (NBTI) in a sense amplifier, the method comprising:
storing first and second data signals using corresponding first and second inverter circuits in a latch, wherein
a supply voltage path of the first inverter circuit is coupled to a drain of a first NBTI compensation transistor, and
a supply voltage path of the second inverter circuit is coupled to a drain of a second NBTI compensation transistor;
coupling a gate of the first NBTI compensation transistor to a data node of the first inverter circuit when the latch is in a hold state, and
coupling a gate of the second NBTI compensation transistor to a data node of the second inverter circuit;
coupling the gate of the first NBTI compensation transistor and the gate of the second NBTI compensation transistor to a ground potential when the latch is in a sense state; and
coupling a supply voltage bias circuit between the first and second NBTI transistors and a supply voltage of the sense amplifier, wherein the supply voltage bias circuit is coupled between the first and second NBTI transistors and the supply voltage by:
coupling a source electrode of a first supply voltage bias transistor to the supply voltage,
coupling a drain electrode of the first supply voltage bias transistor to the source electrode of the first NBTI transistor and the source electrode of the second NBTI transistor,
coupling a gate electrode of the first supply voltage bias transistor to receive an enable signal,
coupling a source electrode of a second supply voltage bias transistor to the supply voltage,
coupling a drain electrode of the second supply voltage bias transistor to the source electrode of the first NBTI transistor and the source electrode of the second NBTI transistor, and
coupling a gate electrode of the second supply voltage bias transistor to the drain electrode of the first and second source voltage bias transistors.
18. The method of claim 17 further comprising:
providing the first and second data signals from a one-time programmable memory cell.
19. A method for compensating for negative bias temperature instability (NBTI) in a sense amplifier, the method comprising:
storing first and second data signals using corresponding first and second inverter circuits in a latch, wherein
a supply voltage path of the first inverter circuit is coupled to a drain of a first NBTI compensation transistor, and
a supply voltage path of the second inverter circuit is coupled to a drain of a second NBTI compensation transistor;
coupling a gate of the first NBTI compensation transistor to a data node of the first inverter circuit when the latch is in a hold state, and
coupling a gate of the second NBTI compensation transistor to a data node of the second inverter circuit;
coupling the gate of the first NBTI compensation transistor and the gate of the second NBTI compensation transistor to a ground potential when the latch is in a sense state;
enabling an equilibration device coupling the drains of the first and second NBTI compensation transistors when the latch is in the hold state; and
disabling the equilibration device when the latch is in the sense state.