Zero leakage, high noise margin coupled giant spin hall based retention latch

A data retention system comprising:

• a first volatile data latch configured to store complementary volatile charge states;
• a status indicator configured to generate a sleep signal and a wake signal based on a power mode of the data retention system;
• a non-volatile data retention circuit comprising:
• a coupled giant spin hall latch configured to generate and store complementary non-volatile spin states corresponding to the complementary volatile charge states of the first volatile data latch in response to receiving a charge current from the first volatile data latch, and to generate a differential charge current signal corresponding to the complementary non-volatile spin states in response to application of a read voltage;
• a write switch configured to selectively enable flow of the charge current from the first volatile data latch to the coupled giant spin hall latch in response to the sleep signal;
• and
• a read switch configured to selectively enable the application of the read voltage to the coupled giant spin hall latch in response to the wake signal;
• and
• a second volatile data latch configured to read the complementary non-volatile spin states from the non-volatile data retention circuit at power on.

A method of retaining complementary volatile charge states of a volatile data latch when powered down, the method comprising:

• receiving a sleep signal indicative of initiation of power down mode from a status indicator;
• and
• in response to receiving the sleep signal:
• coupling, via a write switch, output nodes of the volatile data latch to opposite ends of a giant spin hall metal of a coupled giant spin hall latch to receive a charge current from the volatile data latch through the giant spin hall metal;
• applying a voltage to first and second spin transfer torque (STT) stacks of the coupled giant spin hall latch, the first and second STT stacks being at opposite sides of the giant spin hall metal;
• and
• generating and storing, by the coupled giant spin hall latch, complementary non-volatile spin states corresponding to the complementary volatile charge states of the volatile data latch in response to receiving the charge current from the volatile data latch.

A method of restoring complementary volatile charge states of a volatile data latch when powering up, the method comprising:

• receiving a wake signal indicative of initiation of power up mode from a status indicator;
• and
• in response to receiving the wake signal:
• coupling, via a read switch, a giant spin hall metal of a coupled giant spin hall latch to a low voltage;
• coupling ends of first and second spin transfer torque (STT) stacks of the coupled giant spin hall latch not adjacent to the giant spin hall metal to a read voltage;
• and
• generating a differential charge current signal corresponding to complementary non-volatile spin states stored in the first and second STT stacks, in response to applying the read voltage.