PCF8563 RTC time became 1970

[jingKang]

Hi all, 

I have recently encountered a problem with PCF8563T(Real Time Clock). ,Most of the time, RTC works well，When the power is turned off and restarted, there is a small probability that the RTC time became 1970，It's like the battery power supply is interrupted，But I have added a XH414H capacatir and a CR1220 battery，at this time, the RTC battery voltage is 2.9V，

 I'd be grateful if someone would clarify what could be possibly wrong with my board

[jingKang]

I'm so sorry that I haven't replied for I've been traveling for half a year

This issue takes a few days to occur, so it is difficult to test the VCC3V3/battery/CLCKOUT waveform  at the time of issue happened。These signals are normal as usual when the RTC works well。

We only use battery to suport the RTC, after 5 days of power on and off test, the problem still appeared

Does the I2C-bus clock affect reset?

We change the clock to 400KHz, It works well for 2 months with power on and off test

And we set the Control registers(address 00h)  bit3 to 0 to disable the Power-On Reset, the issue happened again

[guoweisun]

When you switch the power supply from VCC3V3 and Battery, there should be a power on reset happened on RTC.

You can test the VCC3V3/battery/CLCKOUT waveform to confirm when issue happened.

[guoweisun]

Can you share with your schematic?

[jingKang]

Thank you  for your reply

this is my schematic