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4013 and 4017 output behaviour

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georgetwo

Member
hi

we all know the output pins of a 4017 and 4013 ic. for a long time, i have noticed that:
the clk input of both ics are sensitive to signals. But it does not remember its former state (on or off) when power is removed from the circuit and placed back again after some time.
question:

is there any way i can make it remember its former state when power is interupted? any circuit diagram that can help solve the situation?
I need your help
 

sheldonstv

New Member
as far as the 4017 goes pin 15 being the reset terminal (active hi to reset it)you can only get it to reset with the 1st output Q0 upon repowering the ic,and the 4013 needs to have its power on reset as well so the outputs are in a set state on switch on........
 

Mikebits

Well-Known Member
Reset pin on power up, after that you must control its state. Perhaps software can reset if hardware goes out of control.
 

crutschow

Well-Known Member
Most Helpful Member
The only way to have those chips stay in a particular state is to provide a battery backup to the chips when they are otherwise unpowered. CMOS chips take only microamps of current when in a static state so a small battery will power them for months or even years.

You could use two diodes to isolate the power to the chips from the supply and the battery. If you are concerned about the drop of the diodes you can minimize that by using schottky diodes. The battery voltage should be less than the normal supply voltage so that the supply powers the circuit when it's on (to maintain their state you just need a voltage that's above the minimum rated voltage for the chip).
 
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fernando_g

New Member
As Crutschow mentions, CMOS circuits draw microscopic amounts of current if they are not being clocked, and can maintain its actual state well below 3 volts. However, no load should be drawn from any of its outputs for this statement to be true.
Thus, one of those lithium coin cells, isolated with a low drop schotky, will do the trick.
 
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