ST Micro's new Real Time Clocks (RTCs) comes precalibrated from the factory. The MT41T83 and MT41T93 are calibrated to +/- 5 ppm. The calibration is done by setting a internal load capacitance and are set to accuracy of 12 seconds per month.
MT41T93 has 10 MHz SPI bus and MT41T83 has 400 kHz I2C interface. The other common features on both the chips are, analog calibration, programmable auto-reload counter/timer, dual alarms, low 450nA backup current, 12 bytes of NVRAM, oscillator fail detection, programmable square wave generator and a watchdog.
The lowest operating voltage they can work upto is 1.8V.
If you don't require programmable square wave generator, watchdog and alarm you can go for MT41T82.
Availability: Sampling now
Listed price: MT41T82 - $0.70 each in volumes (without factory calibration)
MT41T83/93 - $0.90 each in volumes (without factory calibration)
MT41T83/93 - $1.20 each in volumes (with factory calibration)