Ultra-low-power variation-tolerant radiation-hardened cache design
A random access memory (RAM) cell provides a control section and a storage section coupled to the storage section. The storage section includes complementary metal-oxide semiconductor (CMOS) transistors and the storage section is read by precharging the control section to a virtual drain voltage.
1. A Four-Transistor (4T) random access memory (RAM) cell cache comprising:
(a) a 4T RAM cell comprising:
(1) a first transistor of a first conduction type;
(2) a second transistor of a second conduction type, wherein the first transistor and the second transistor comprise a transmission gate;
(3) a third transistor having a gate electrode coupled to the transmission gate and a source electrode coupled to a read control line for storing and reading a logic value in the 4T RAM cell; and
(4) a fourth transistor, coupled to the third transistor to reduce leakage current through the third transistor; and
(b) error correcting codes (ECC) configured to permit a single upset to occur per cache-line per refresh cycle.
2. The 4T RAM cell cache, of claim 1 , wherein the 4T RAM cell is stacked with at least one more 4T RAM cell on a common Read Bit Line (RBL).
3. The 4T RAM cell cache of claim 1 , wherein the logic value is further stored in a diffusion capacitance of the first transistor and the second transistor.
4. The 4T RAM cell cache of claim 1 , wherein the 4T RAM cell operates at voltages below a threshold voltage for the first transistor.
5. The 4T RAM cell cache of claim 4 , wherein the 4T RAM cell operates at voltages below the threshold voltage for the first transistor, and below a second threshold voltage for the second transistor.
6. The 4T RAM cell cache of claim 5 , wherein the 4T RAM cell operates at voltages below the threshold voltage for the first transistor, the second threshold voltage for the second transistor, and a third threshold voltage for the third transistor.
7. The 4T RAM cell cache of claim 6 , wherein the 4T RAM cell operates at voltages below the threshold voltage for the first transistor, the second threshold voltage for the second transistor, the third threshold voltage for the third transistor, and a fourth threshold voltage for the fourth transistor.
8. The 4T RAM cell cache of claim 4 , wherein the threshold voltage is a 400 mV deviation from zero volts.
9. The 4T RAM cell cache of claim 1 , further comprising a sense amplifier section, coupled to the storage section, for sensing the logic value stored in the 4T RAM cell.
10. The 4T RAM cell cache of claim 1 , wherein the transmission gate passes a logical 1 as a supply voltage level.