This document describes the STMicroelectronics line of non-volatile SRAMs (NVRAMs) known as ZEROPOWER® or TIMEKEEPER® NVRAMs, supervisors, and serial RTCs which offer the best of both worlds: memory devices that are non-volatile like EEPROM, yet have the fast access of SRAM. The document also describes how the NVRAM works and how to predict its battery life.
This document provides a guide for predicting the battery life and data retention period of STMicroelectronics non-volatile SRAMs (NVRAMs) and serial real-time clocks (RTCs). It covers the technology behind the devices, including standard SRAM, EEPROM, and Flash memory comparisons, as well as the specific characteristics of ST's ZEROPOWER and TIMEKEEPER product families.
The text details the battery technology used, specifically the BR1225 and BR1632 lithium button cells, and explains how to calculate storage life and capacity consumption under various operating conditions. It includes data for different product categories such as 4T and 6T SRAM cells, hybrid devices, supervisors, and industrial temperature variants.
| Battery Capacity (BR1225) | 48 mAh |
|---|---|
| Battery Capacity (BR1632) | 120 mAh |
| Nominal Battery Output | 2.9 V |
| Data Retention Guarantee (EEPROM) | 10 years |
| Data Retention Current (6T devices) | less than 150 nA at 70 °C |
STMicroelectronics uses the BR1225 and the BR1632 lithium button cell batteries.
Both the BR1225 and BR1632 cells produce a nominal 2.9 V output.