Latching circuit with delay.

Thread Starter

VahagnZ

Joined Jun 27, 2022
3
Hello everyone. I have a small problem and need some help. I want to design latching circuit. And turn on my circuit when B1 pressed more than 5 second. And if it is pressed shorter than 5 second, it will not connect.
 

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crutschow

Joined Mar 14, 2008
30,100
The red transistor (please label all the parts) needs to be a PNP, not an NPN, with it's emitter connected to the battery voltage.

What is the battery voltage?

What is the maximum current required by the buck enable signal?
 

Thread Starter

VahagnZ

Joined Jun 27, 2022
3
okay I have seen that put wrong transistor. Battery is 2 cell 18650 I think average voltage will be 7.4v․
In IC datasheet I have find only this parameter about (Enable Pull Up Current 1 -- μA)
 

crutschow

Joined Mar 14, 2008
30,100
Below is the LTspice simulation of the circuit:
I changed the NPNs to small N-MOSFETs, since they have sharper switching characteristics.
You may need to tweak the value of R2 to get the desired delay, due to the tolerance on the MOSFET's gate threshold voltage.

Does that do what you want?

1656441898917.png
 
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