AN53313 - Real Time Clock Calibration in Cypress nvSRAM | Cypress Semiconductor
AN53313 - Real Time Clock Calibration in Cypress nvSRAM
AN53313 describes the Real Time Clock (RTC) calibration feature in Cypress nvSRAM that helps to maintain precise system time by compensating for the crystal frequency error.
The Real Time Clock (RTC) in Cypress nvSRAM is driven by a crystal oscillator, with an external crystal having a nominal frequency of 32.768 kHz. Most 32.768-kHz crystals have a frequency tolerance of ±20 parts per million (ppm) at +25 °C. This frequency tolerance results in timing error over a long period of time. For example, a crystal with 20-ppm error in nominal frequency can drift the clock accuracy by 52 seconds in a month. You can compensate this drift by using the calibration feature in the nvSRAM RTC.