TIME CLOCK CALCULATOR SOFTWARE

To calculate the typical and worse case data retention lifetimes, select the Supervisor Device and Battery Type in the form below. The available battery capacity for the SNAPHAT В® of your choice can then be divided by this current to determine the amount of data retention available (48mAh or 120mAh). The data retention current value of the SRAMs can then be added to the Ibat value of the Supervisor to determine the total current requirements for data retention. Manufacturers generally specify a typical condition for room temperature along with a worst case condition (generally at elevated temperatures.) The system level requirements will determine the choice of which value to use. Most SRAMs specify data retention current (IccDR) at 3.0V. If data retention lifetime is a critical parameter for the system, it is important to review the data retention current specifications for the particular SRAMs being evaluated. TIMEKEEPER digital calibration (with the exception of the M48T86 device which does not have a calibration register) employs periodic counter correction to add or subtract counts from the oscillator divider circuit and hence compensate for temperature or crystal variations.

Without calibration a typical TIMEKEEPER device is accurate to В± 1.53 minutes (В± 35 ppm) per month at 25вЊ. TIMEKEEPER products are driven by a quartz crystal controlled oscillator with a nominal frequency of 32,768Hz.

TIME CLOCK CALCULATOR SOFTWARE

The digital calibration feature of STMicroelectronics TIMEKEEPER products enables frequency calibration of the device to be software controlled.

Application Note AN934, TIMEKEEPER Calibration.

Time clock calculator