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# Problem about POR(power-on reset)

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#### ry257

##### Newbie level 3
In my digital circuit ,the low voltage is 1v,not 0v,so when it is power off and restart ,my POR circuit doesn't give a reset signal.
In other words,when digital circuit change from 1v to 5v(high voltage),my POR doesn't work.how to solve it?
any papers ,patents about it?
thanks!!!

Why your POR should give a signal. Power is not disappeared. If you need behavior like you mentioned you need another circuit - low voltage detector and OR/AND it's output with your POR.

you can design a comparator to monitor the voltages

Can u tell me your power on and power off time first as it will affect your solution.
Your problem is very challenging and I am resolving it as well for a long time, if you need a zero DC current POR design. Otherwise, it can be much easier if you can have non-zero DC current POR.

1V is a problem? My power on circuit has one when power is more than 2V. as power off is. the schematic is the most normal.

watersky,

you are not to the point. We talk about POR malfunction when power is off but not off in the zero voltage and restart power again.
You can simulate your POR and I bet it will fail POR next time

the most difficult case is *power fluctuation* when the battery is getting old (higher output resistance). Look up power-on reset in google... add austria microsystems to the search and you'll hit a nice paper on this.

Sometimes por work after the bandgap, sometimes por begin to work because of the rise of the Vsupply. So two kinds of por is different, there are different kinks of solution to them.

hi..
As what i understand, the POR block will be connected to some flops or other digital blocks, so the Vthreshold of POR block is important to make sure it will be higher than Vih of the digital circuit which connected to POR. Please correct me if i make mistakes.
i would like to ask, the Vih of those digital circuit should be able to search just through online? Since we are using only standard cell for digital circuitry.
Thanks very much for any advice on this as i am still new to design

when power off ,in my schematic there is a pmos that makes voltage of cap in por circuit decrease. so my circuit is ok when restart my circuit.

the POR block just give a edge pulse, why it can not work? most time ,just because of the no enough delay. can you give more detail of you circuit?

ry257 said:
In my digital circuit ,the low voltage is 1v,not 0v,so when it is power off and restart ,my POR circuit doesn't give a reset signal.
In other words,when digital circuit change from 1v to 5v(high voltage),my POR doesn't work.how to solve it?
any papers ,patents about it?
thanks!!!

PLEASE GIVE THE CIRCUIT FOR POR,SO THAT ICAN HELP

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