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VBAT and 32.76kHz oscillator doubt

Question asked by Gabriele Marocco on Nov 9, 2012
Latest reply on Nov 9, 2012 by Puebla Palma Luis

I don't understand why while the TWR-K20D50 board is powered by USB (J36 is open) and no battery is inserted, the demo program works only if J35 is closed.

From the datasheet of the microcontoller I have understood that Vbat powers only the RTC clock but the test on the evaluation board shows the opposite: is Vbat necessary for the system (and not only for the RTC module) in order to work properly?


What about the 32.768kHz crystal? Is it necessary if I don't want to power the RTC oscillator and if a 8MHz resonator feeds the system clock?