The CMOS bq4010/Y/LY is a nonvolatile 65,536-bit static RAM organized as 8,192 words by 8 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 supply for an out-of-tolerance condition. When the voltage VCC (overline) falls out of tolerance, the SRAM is unconditionally write-protected to prevent an inadvertent write operation.
At this time the integral energy source is switched on to sustain the memory until after the voltage VCC returns valid.
The bq4010/Y/LY 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.
The bq4010/Y/LY requires no external circuitry and is compatible with the industry-standard 64-Kb SRAM pinout.
When power is valid, the bq4010/Y/LY operates as a standard CMOS SRAM. During power-down and power-up cycles, the bq4010/Y/LY acts as a nonvolatile memory, automatically protecting and preserving the memory contents.
The internal coin cells used by the bq4010/Y/LY have an extremely long shelf life and provide data retention for more than 10 years in the absence of system power.
As shipped from TI, the integral lithium cells of the MT-type module are electrically isolated from the memory. (Self-discharge in this condition is approximately 0.5% per year.) Following the first application of the voltage VCC, this isolation is broken, and the lithium backup provides data retention on subsequent power-downs.
TI BQ4010YMA-150