bq2502

Note: Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Functional operation should be limited to the Recommended DC Operating Conditions detailed in this data sheet. Exposure to conditions beyond the operational limits for extended periods of time may affect device reliability.

The CMOS bq2502 Integrated Backup Unit provides all the necessary functions  for converting one or two banks of standard CMOS SRAM into nonvolatile read/write memory.

A precision comparator of bq2502 monitors the 5V VCC input for an out-of-tolerance condition.When out of tolerance is detected, the two conditioned chip-enable outputs are forced inactive to write-protect both banks of SRAM.

Power for the external SRAMs is switched from the VCC supply to the internal battery-backup supply as VCC decays. On a subsequent power-up, the VOUT supply is automatically switched from the internal lithium supply to the VCC supply. The external SRAMs are write-protected until a power-valid condition exists. The reset output provides power-fail and power-on resets for the system.

During power-valid operation, the input decoder of bq2502 selects one of two banks of SRAM.

The internal lithium cell is initially electrically isolated, protecting the battery from accidental discharge. Connection to the battery is made only after the first application of VCC.