I have to design a power supply with the LTC1707. It have a enable input to control it.
Now I have to enable an disable this switching supply with a push button.
Only when I push in button during five second, enable = 1.
And if I push a button during five second again, enable = 0.
I have made a schematic with a Flip Flop, but it is instantaneous, i need five seconds.
Is it possible to make this function without microcontroller ? Do you have any idea?
Thanks, sorry for my english…
EDIT:
Thanks a lot for your help! After some research and test on Proteus, i have made a smallest schematic ! :
Best Answer
This should work:
If you have some glue logic you can use for U2, use that. If you don't, D1 D2 R5 will do the same thing.
CIRCUIT DESCRIPTION
S1 is a single-pole single-throw normally open momentary switch, U1A and U1B are the two halves of a dual monostable multivibrator, U2 is an AND gate, and U3 is a "D" type flip-flop.
When Vcc is first connected, U1 and U3 will be held low by C3, resetting them until C3 charges up through R4 and goes positive enough to release the resets.
When that happens, U1A-Q, U1B-Q, U2-3, and U3-Q will all be low and will remain that way until S1 is made.
When S1 is made, U1A-A will go high, triggering U1 and forcing U1A-Q high for the time set by R2C1, about 5 seconds.
When U1A times out and U1A-Q goes low, that edge will trigger U1B, forcing U1B-Q high for about 100 milliseconds. Then, if S1 is still made when U1B-Q goes high, U2-1 will also be high and U2-3 will go high until either U1B-Q times out or S1 is opened.
U2-3 is connected to the clock input of U3 and, when it goes high, will toggle U3-Q since U3 is wired as a divide-by-two.
With U1A and U1B both timed out, when S1 is opened U1A-A and U2-1 will go low, returning U1 and U2 to their initial states.
If, subsequently, S1 is made and held made for the time it takes U1A and B to time out, U3's clock input will be exercised and it will once again toggle, completing the cycle.