Regarding Battery back-up (VBAT) used in MK70FN1M0VMJ12 for RTC

[puspamnayak]

Hi,

I want to know do i need external logic circuit (OR circuitry) while switching from VDD to VBAT
(coin cell battery for RTC) and vice versa or

switching will happen internally between VDD to VBAT and VBAT to VDD depending on detection of
supply voltage VDD by internal logic in MK70FN1M0VMJ12

Kindly reply at earliest

Thanks and regards,

Puspam N

[puspamnayak · Accepted solution]

Hi Adrian,

Thanks for the clarification. This information will definitely going to help for the projects using freescale microcontroller.

Best and Warm Regards

Puspam Nayak

[egoodii]

Achieved externally with a dual-schottky-diode device like BAT54C.

[puspamnayak]

Thanks Earl. Information will help...

Thanks once again

Regards,

Puspam N

[egoodii]

See also:

How to detect if VBAT supply is present for RTC to work?

[puspamnayak]

Hi Earl,

Thanks for giving this valuable information and for sharing schematic for VBAT hardware connection.

I have a question on this, i am using two K70 micrcontroller on my board. One K70 will have RTC battery back-up using Coin cell and for other K70 we dont need power for RTC so in that case can i keep VBAT pin open or that has to be terminated to ground.

Kindly suggest on this query

Thanks and Regards,

Puspam N

[adriancano]

Hi,

If you are not planning to use the RTC module then you can leave the VBAT pin floating; try to never access to the RTC registers to avoid bus faults and also the RTC clock gate in the SIM register should it remains in value 0.

Hope this information can help you.

Regards,

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