Retention Voltage Management for a Volatile Memory

An apparatus, comprising:

• a memory circuit including a plurality of sub-arrays, wherein the memory circuit is configured to implement a retention mode according to stored information indicating voltage sensitivities for the plurality of sub-arrays;
• and
• a voltage control circuit coupled to a power supply node, wherein during the retention mode for the plurality of sub-arrays, the voltage control circuit is configured to:
• generate, based on the stored information, a first retention voltage level for a first subset of the plurality of sub-arrays;
• and
• generate, based on the stored information, a second retention voltage level, higher than the first retention voltage level, for a second subset of the plurality of sub-arrays;
• and
• wherein the first and second retention voltage levels are lower than a power supply voltage level of the power supply node, and wherein the second subset includes one or more voltage sensitive data storage cells that fail to retain data at the first retention voltage level.

A method comprising:

• coupling, by a voltage control circuit, a power supply node to a plurality of sub-arrays included in a memory circuit;
• during activation of a retention mode for the memory circuit:
• de-coupling, by the voltage control circuit, the plurality of sub-arrays from the power supply node;
• generating, by the voltage control circuit using stored information, a first retention voltage level for a first subset of the plurality of sub-arrays;
• and
• generating, by the voltage control circuit using the stored information, a second retention voltage level, higher than the first retention voltage level, for a second subset of the plurality of sub-arrays;
• and
• wherein the first and second retention voltage levels are lower than a power supply voltage level of the power supply node, and wherein the second subset includes one or more voltage sensitive data storage cells that fail to retain data at the first retention voltage level.

A memory circuit, comprising:

• a plurality of sub-arrays, including respective pluralities of data storage cells, configured to retain data values when a retention mode is active;
• a voltage control circuit configured to:
• couple the plurality of sub-arrays to a power supply node;
• during activation of the retention mode:
• decouple the plurality of sub-arrays from the power supply node;
• using stored information, generate a first retention supply signal for a first subset of the plurality of sub-arrays, wherein a voltage level of the first retention supply signal is less than a voltage level on the power supply node;
• and
• using the stored information, generate a second retention supply signal for a second subset of the plurality of sub-arrays, wherein a voltage level of the second retention supply signal is greater than the voltage level of the first retention supply signal and less than the voltage level on the power supply node;
• and
• wherein the second subset includes one or more voltage sensitive data storage cells that fail to retain data at the voltage level of the first retention supply signal.