This application note describes the benefits of using SPI nvSRAM in metering applications and is aimed at designers and architects of the latest 'smart' electrical energy meters.
Introduction
Cypress's nvSRAM is a proven, established combination of fast SRAM cells and silicon-oxide-nitride-oxide-silicon (SONOS)-based nonvolatile memory cells. You can rapidly transfer the entire contents of the SRAM to nonvolatile storage automatically (AutoStore) if the power supply fails, or transfer on demand by issuing the relevant software command (Software Store). The nvSRAM requires a small (typically 47 uF) capacitor connected to its VCAP pin to complete its AutoStore operation. When the main power supply (VCC) is applied to the nvSRAM, it charges the capacitor connected to its VCAP pin. When the power supply falls below a threshold (VSWITCH), the nvSRAM automatically switches from VCC to VCAP and completes the AutoStore cycle.
