BQ2204A(X4 SRAM Nonvolatile Controller Unit)IntroductionThe CMOS BQ2204A SRAM Nonvolatile 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 selects one of up to four banks of SRAM.FeaturePower monitoring and switching for 3-volt battery-backup applicationsWrite-protect control2-input decoder for control of up to 4 banks of SRAM3-volt primary cell inputsLess than 10ns chip-enable propagation delay5% or 10% supply operationAppearance
