monostable mode timer 555

[yassin.kraouch]

Hi, i want to configure thiis timer https://www.fairchildsemi.com/ds/LM/LM555.pdf
in a monostable configuration, when a trigger pin is lower than 1/3 the output is high, and when a new pulse applied after a short time, the output remains high ( a time is added),
many thanks

 

[HTA]

Page 4 of the data sheet shows this operation.

Enjoy your design work!

 

[yassin.kraouch]

Page 4 of the data sheet shows this operation.

Enjoy your design work!

no in the datsheet it is written : if you trigger again the Trig pin when the output is high you will not extend the output time,

 

[HTA]

that correct. Its not retriggerable like a LS/HC123 monoflop. To make the 555 retriggerable it requires discretes around it. Here is a circuit for it https://www.elektronik-kompendium.de/public/schaerer/retr555.htm with text only in German.

Enjyo your design work!

 

[yassin.kraouch]

thanks, you think that this IC can do the job ? instead of using 555 timer+external component ? https://www.onsemi.com/pub_link/Collateral/MC14538B-D.PDF

 

[yassin.kraouch]

any help please ?

 

[HTA]

It is retriggerable. The external component needs to be calculated based on your need(T= Rx * Cx).

Enjoy your design work!

 

[yassin.kraouch]

what do you recommend. the retriggebae IC with 16 pin or using the 555 with external components ?

 

[HTA]

It is your decision. I personally would take a retriggerable monoflop since it is designed for that.

Enjoy your design work!