nRF52833-DK question

[harrykuang]

I have a question regarding the power sequence mentioned in the nRF52833-Dk guide:

or the power sources section the guide explains it as:

 

 

I drew the body diode of U15 as shown. If I put 1.8V on P21, in the beginning of time about 1.1V (1.8V minus the body diode drop) will appear on Vsupply which powers the AND gate U25. U25 has a minimum Vcc of 1.65V. How does this guarantee that it will behave properly? I am sure I am missing something here.

Harry

[ketiljo]

You're partly right in your analysis. The diode drop will be far less than 0.7 V when the current draw is low. So the AND gate will have just enough voltage to operate in the few ns before it can fully turn on the switch. I agree that it's not optimal.