Capacitor backup for SRAM
Embodiments of the disclosure provide a method for backing up data in an SRAM device, and an SRAM device that includes a capacitive backup circuit for backing up data in an SRAM device. The method may include writing data to the SRAM cell by applying an input voltage to set an input node of cross-coupled inverters to a memory state. The method may also include backing up the data written to the SRAM cell by electrically coupling the input node to the capacitive backup circuit. The method may also include restoring the data stored in the capacitive backup circuit to the SRAM cell by electrically coupling the capacitive backup circuit to the input node.
1. A method of backing up a Static Random Access Memory (SRAM) cell on an SRAM device to a capacitive backup circuit of the SRAM cell, the method comprising:
backing up the data written to the SRAM cell by:
electrically coupling an input node of cross-coupled inverters to a capacitor of the capacitive backup circuit by turning on backup switch configured in a series connection between the capacitor and a feedback switch, wherein the capacitive backup circuit is not in a feedback circuit formed by a first CMOS inverter and a second CMOS inverter; and
restoring the data stored in the capacitive backup circuit to the SRAM cell by:
deactivating an input voltage to the SRAM cell,
deactivating the feedback switch, wherein the feedback switch is in the feedback circuit and different than the backup switch, and
electrically coupling the capacitive backup circuit to the input node in response to deactivating the feedback switch.
2. The method of claim 1 , further comprising writing data to the SRAM cell by applying an input voltage to set the input node of cross-coupled inverters to a memory state.
3. The method of claim 2 , wherein writing data includes turning off a feedback switch to break cross-coupling of the cross-coupled inverters.
4. The method of claim 1 , wherein the backing up the data includes storing data from the cross-coupled inverters at a time later than a time the data was backed up.
5. The method of claim 1 , further comprising retaining the data in the capacitor of the capacitive backup circuit by turning off the backup switch on the capacitive backup circuit.