The M40SZ100W NVRAM controller is a self-contained device which converts a standard low-power SRAM into a non-volatile memory. A precision voltage reference and comparator monitors the VCCinput for an out-of-tolerance condition.

When an invalid VCCcondition occurs, the conditioned chip enable output (ECON)is forced inactive to write protect the stored data in the SRAM. During a power failure, the SRAM is switched from the VCCpin to the external battery to provide the energy required for data retention. On a subsequent power-up, the SRAM remains write-protected until a valid power condition returns.