Time deviation in PCF8563TS/4

[JoeChen]

Recently, we are using a PCF8563TS/4, and we have tested it.

The working temp. is around 25℃, and the schematic of the design is attached.

We have run it for a day with power and found that the time deviation is -5 seconds/day which is quite worse. 

Please help us to check the schematic and let us know what could we do to improve it.

As we know, the time deviation of this RTC should be ±5mins/year

[TomasVaverka]

Hi Joe,

Please take a look at the User Manual UM10301 that describes among others how to match the crystal with the RTC oscillator.

The RTC accuracy is essentially dependent on the tolerance of the used crystal (also how sensitive it is to temperature variations) and its matching to the oscillator.

For example if the load capacitance presented to a crystal is smaller than what the crystal was designed for, the oscillation frequency will be too high and thus if used with an RTC, the clock will run too fast.

Best regards,

Tomas