bq4025

The CMOS bq4025 is a nonvolatile 4,194,304-bit static RAM organized as 262,144 words by 16 bits. The integral control circuitry and lithium energy source provide reliable nonvolatility coupled with the unlimited write cycles of standard SRAM.

The control circuitry of bq4025 constantly monitors the single 5V supply for an out-of-tolerance condition. When VCC falls out of tolerance, the SRAM is unconditionally write-protected to prevent inadvertent write operation.

At this time the integral energy source of bq4025 is switched on to sustain the memory until after VCC returns valid. The bq4025 uses extremely low standby current CMOS SRAMs, coupled with small lithium coin cells of bq4025 to provide nonvolatility without long write-cycle times and the write-cycle limitations associated with EEPROM. The bq4025 requires no external circuitry and is compatible with the industry-standard 4Mb SRAM pinout.