FEATURES
® Data retention in the absence of power ® Automatic write-protection during power-up/power-down cycles ® Industry-standard 40-pin 128K x 16 pinout ® Conventional SRAM operation; unlimited write cycles ® 10-year minimum data retention in absence of power ® Battery internally isolated until power is applied GENERAL DESCRIPTION
The CMOS bq4024 is a nonvolatile 2,097,152-bit static RAM organized as 131,072 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 constantly monitors the single 5V supply for an out-of-tolerance condition. When VCC falls out of tolerance, the SRAM is unconditionally writeprotected to prevent an inadvertent write operation. At this time the integral energy source is switched on to sustain the memory until after VCC returns valid. The bq4024 uses extremely low standby current CMOS SRAMs, coupled with small lithium coin cells to provide nonvolatility without long write-cycle times and the write-cycle limitations associated with EEPROM.
