Real-Time Calendar
for Portable or Managed Power Applications
A Real-Time Calendar can be used for an alarm clock, data logging, or any applications that require time and date stamp information.
By combining the Calendar with Fusion, you can control the power and operation of your entire system for power cycle timers etc. Actel Fusion® is the world's first mixed-signal FPGA, integrating configurable analog, a real-time counter (RTC), flash memory blocks, and clock generation circuits — all in a single chip. Fusion can be used to manage power sequencing and ramp-rate for all supplies in your system. Using the Fusion device's RTC, this application provides a count of seconds, minutes, hours, day of the week, day of the month, month, and year. The month-ending date is automatically adjusted for months with less than 31 days, including corrections for leap years. Moreover, the FPGA core can be turned off to save power, and the RTC will continue to keep track of the time and date information.
Using a 32.768 Hz crystal oscillator, with built-in prescaler, provides a 256 Hz input to the Real-Time Counter, which gives the 8th bit a 1 Hz frequency. The 40-bit counter can count for over 136 years.
A single 3.3 V supply into the device drives the 1.5 V regulator, which is used to power the FPGA logic. The regulator can turn off power to the FPGA core with the RTC still running, so it can continue to track time until the device wakes up. For low-power applications, the Fusion device with crystal oscillator and RTC running pulls approximately 200 ľA. The device can be signaled to wake up from an external trigger through the PUB pin or from a match being reached within the counter.
