RTC chips traditionally were the domain of Maxim and NXP. Switzerland-based MicroCrystal recently made quite a buzz with its RV-8803, which offers simple integration, an I2C interface and extreme accuracy.
Let us start out by looking at a system overview. Figure one shows how this I2C RTC is made up internally – interested observers note that we are looking at a real time clock IC with an integrated crystal. This is beneficial in that the amount of space on the PCB is limited – the smallest component, after all, is one which does not need to be placed at all.
MicroCrystal provides an integrated crystal in its RTC IC…
The housing of the chip is calibrated via a thermal sensor which permanently monitors the ambient temperature. MicroCrystal uses this technology to achieve impressive degrees of accuracy – in the range from -40 to 85 degrees celsius, a timing accuracy of but 3ppm is to be observed. As thje part does not, however, use a heater, it can make do with but 240nA of current.
Users of the Epson RX-8803SA/LC families will be happy to find out that the part shown in figure two is a second source – its register set is completely compatible with this once-famous Japanese real time clock. Furthermore, a clock output lets third-party ICs “parasite” away from the high accuracy signal generated inside the part.
…While the pinout is simple, the housing is very small
Sadly, keep in mind that the housing of the part is extremely small and can not (really) be hand soldered. However, various developer and evaluation kits are available – they are available from various sources.
One interesting aspect of MicroCrystal involves the nomenclature – with them, a datasheet is but two pages long. The actual datasheet information goes by the name application manual, and can be found by visiting here.