Minimum voltage required at VCAP pin to complete AutoStore?

Question:

What is the minimum voltage required at VCAP pin to complete AutoStore?

 

Answer:

 

Response: The minimum voltage at VCAP pin for proper circuit operation is 2V

Explanation:

During power down, VCAP provides the energy to perform the STORE operation. The way AutoStore is executed is as follows: When VCC falls below the VSWITCH value (which is 2.65V), power to the internal circuits gets switched from VCC power to VCAP power and a STORE operation (AutoStore) is initiated. This operation consumes an average current, ICC4, as specified in the datasheet. The minimum voltage for the store circuit to operate is 2V. Therefore, the VCAP pin voltage should not be lower than 2V, before the STORE is completed. In other words, the VCAP pin voltage should not fall below 2V for the duration of the tSTORE time (=8ms) after VCC crosses VSWITCH level. In the nvSRAM datasheets, the specification limits for VCAP value has taken this into account and hence this voltage is not a user consideration when designing with nvSRAMs.