Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

pulse width stretching

Status
Not open for further replies.

iaf

Member level 3
Joined
Apr 11, 2019
Messages
55
Helped
0
Reputation
0
Reaction score
0
Trophy points
6
Activity points
416
i want to design a circuit for stretching the "0" output of my signal. I have seen the Monostable multivibrator but it stretches the "1" output. is there anyway flipping it or another topology for realizing that?
 

barry

Advanced Member level 5
Joined
Mar 31, 2005
Messages
4,860
Helped
1,068
Reputation
2,146
Reaction score
1,053
Trophy points
1,393
Location
California, USA
Activity points
26,527
Could you give us more information? Is this a digital system? Is there a clock? You could use a schmitt-trigger AND gate where the signal goes directly to one input and through an RC to the other input.

"Is there anyway of flipping it?" Of course; use an inverter.
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
46,988
Helped
13,938
Reputation
28,124
Reaction score
12,576
Trophy points
1,393
Location
Bochum, Germany
Activity points
273,976
In addition, most monostable chips have trigger inputs for both polarities. Pulse stretching refers to retriggerable monoflop, otherwise the pulse width would be also limited.
 

iaf

Member level 3
Joined
Apr 11, 2019
Messages
55
Helped
0
Reputation
0
Reaction score
0
Trophy points
6
Activity points
416
Could you give us more information? Is this a digital system? Is there a clock? You could use a schmitt-trigger AND gate where the signal goes directly to one input and through an RC to the other input.

"Is there anyway of flipping it?" Of course; use an inverter.
it's a digital output of a d-flipflop which is clocked by a 50MHz clock. Adding an inverter will invert the "1" to "0" which is not the goal.
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
46,988
Helped
13,938
Reputation
28,124
Reaction score
12,576
Trophy points
1,393
Location
Bochum, Germany
Activity points
273,976
Adding an inverter will invert the "1" to "0" which is not the goal.
barry answered your question in post #1 (how can we use a monoflop with inverse input polarity), you apparently forgot your question.
 

iaf

Member level 3
Joined
Apr 11, 2019
Messages
55
Helped
0
Reputation
0
Reaction score
0
Trophy points
6
Activity points
416
In addition, most monostable chips have trigger inputs for both polarities. Pulse stretching refers to retriggerable monoflop, otherwise the pulse width would be also limited.
I#m designing the circuit so i don't have a ready to use multivibrator
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
46,988
Helped
13,938
Reputation
28,124
Reaction score
12,576
Trophy points
1,393
Location
Bochum, Germany
Activity points
273,976
I#m designing the circuit so i don't have a ready to use multivibrator
Fine, than just design it with correct polarity and don't forget the retrigger point if you expect input pulses longer than the monoflop period.
 

iaf

Member level 3
Joined
Apr 11, 2019
Messages
55
Helped
0
Reputation
0
Reaction score
0
Trophy points
6
Activity points
416
Could you give us more information? Is this a digital system? Is there a clock? You could use a schmitt-trigger AND gate where the signal goes directly to one input and through an RC to the other input.

"Is there anyway of flipping it?" Of course; use an inverter.
sorry didn't get it. am i supposed to have two inputs?
 

iaf

Member level 3
Joined
Apr 11, 2019
Messages
55
Helped
0
Reputation
0
Reaction score
0
Trophy points
6
Activity points
416
Fine, than just design it with correct polarity and don't forget the retrigger point if you expect input pulses longer than the monoflop period.
how do i change the polarity? i just want to extend the 0 output for some ms as an example. The design i used was a NOR gate connected to a capacitor and resister with an inverter in the end giving the output
 

summitville

Member level 3
Joined
Dec 16, 2009
Messages
54
Helped
15
Reputation
30
Reaction score
14
Trophy points
1,288
Location
USA
Activity points
1,668
Low Going Pulse Stretcher using two NAND Gates ...
NAND_GATE
scroll down for schematic
Use "High Speed" and right hand device, best if, "Schmidt Trigger" Input
Width of trigger pulse must be wider than gate delays


Or use something like 74AHC123A or 74AHCT123A Monostable ...
MONO-STABLE
Has both Rising Edge & Falling Edge Triggers

- - - Updated - - -

Can your Low-Going Pulse discharge a small Capacitor ?

Stretch.jpg
 
Last edited by a moderator:
  • Like
Reactions: iaf

    iaf

    points: 2
    Helpful Answer Positive Rating

barry

Advanced Member level 5
Joined
Mar 31, 2005
Messages
4,860
Helped
1,068
Reputation
2,146
Reaction score
1,053
Trophy points
1,393
Location
California, USA
Activity points
26,527
Bad idea. Use this:

stretch.jpg

Have to consider pulse width, etc. in selecting RC. Can also put diode across R for narrow input pulse.
 
  • Like
Reactions: iaf

    iaf

    points: 2
    Helpful Answer Positive Rating

iaf

Member level 3
Joined
Apr 11, 2019
Messages
55
Helped
0
Reputation
0
Reaction score
0
Trophy points
6
Activity points
416
Bad idea. Use this:

View attachment 153653

Have to consider pulse width, etc. in selecting RC. Can also put diode across R for narrow input pulse.
why is it bad idea?
is there any schematic of this schmitt trigger? as i have to design it in that case
 

andre_teprom

Super Moderator
Staff member
Joined
Nov 7, 2006
Messages
9,163
Helped
1,140
Reputation
2,298
Reaction score
1,113
Trophy points
1,403
Location
Brazil
Activity points
53,187
it's a digital output of a d-flipflop which is clocked by a 50MHz clock. Adding an inverter will invert the "1" to "0" which is not the goal.
Would I be wrong in assuming that you are on the scope of a programmable logic circuit design? In this case, it would make little sense to implement this circuit with an analog approach.
 

iaf

Member level 3
Joined
Apr 11, 2019
Messages
55
Helped
0
Reputation
0
Reaction score
0
Trophy points
6
Activity points
416
Would I be wrong in assuming that you are on the scope of a programmable logic circuit design? In this case, it would make little sense to implement this circuit with an analog approach.
no it's actually an analog design just having a digital output
 

barry

Advanced Member level 5
Joined
Mar 31, 2005
Messages
4,860
Helped
1,068
Reputation
2,146
Reaction score
1,053
Trophy points
1,393
Location
California, USA
Activity points
26,527
why is it bad idea?
is there any schematic of this schmitt trigger? as i have to design it in that case
It's a bad idea because you'll never pull the input lower than one diode drop+Vlo of the source. This may not be low enough to effect a logic '0'.
.
 

iaf

Member level 3
Joined
Apr 11, 2019
Messages
55
Helped
0
Reputation
0
Reaction score
0
Trophy points
6
Activity points
416
so how would i design this schmitt trigger with 2 inputs?

- - - Updated - - -

another problem with this design is that the pulse will be stretched in a constant time regardless how long the input takes, which is applicable in case if the input is longer the RC time constant, so is there a solution to add this time constant to the original width?
 

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top