The CMOS bq2204A SRAM Non=volatile Controller Unit provides all necessary functions for converting up to four banks of standard CMOS SRAM into nonvolatile read/write memory.
A precision comparator monitors the 5V VCC input for an out-of-tolerance condition. When out-of-tolerance is detected, the four conditioned chip-enable outputs are forced inactive to write-protect up to four banks of SRAM.
During a power failure, the external SRAMs are switched from the VCC supply to one of two 3V backup supplies. On a subsequent power-up, the SRAMs are write-protected until a power-valid condition exists.
During power-valid operation, a two-input decoder transparently se lects one of up to four banks of SRAM.
► Power monitoring and switching
for 3-volt battery-backup applications
► Write-protect control
► 2-input decoder for control of up
to 4 banks of SRAM
► 3-volt primary cell inputs
► Less than 10ns chip-enable
► 5% or 10% supply operation