Anyone know any good latching IC's?

Thread Starter

magnet18

Joined Dec 22, 2010
1,227
By that I mean, I need an IC that, when an input goes high (set), will make an output high until a different input goes high (the reset)
or, if the set and reset were the same pin, i suppose that would work also
anyone know anything that will work?
The 555 version is being more of a pain than it's worth in troubleshooting and components, I'm just looking for simplicity and reliability right now
 

crutschow

Joined Mar 14, 2008
25,690
You can also make a flip-flop from a pair of NAND or NOR gates or even two inverters or two transistors.
A definition nit--;)

Typically a bistable circuit made from a couple of gates or transistors that immediately responds to a set or reset signal is called a latch. Flip-flop usually refers to a bistable circuit that changes state (as determined by the state of a separate D or JK input) in response to a clock input (although flip-flops often have set and reset inputs that allow them to act as latches).
 

praondevou

Joined Jul 9, 2011
2,942
a 4013 will work, wont it?
Yes. Disable Clock and Data. You can connect them to Gnd.

Note that when using the 4013 both Outputs can be set if you apply for whatever reason a HIGH to SET and RESET.

If that is a problem you can couple the SET / RESET commands via a capacitor to their corresponding inputs. Don't forget the pulldown resistor and a diode in parallel with it.
 

ErnieM

Joined Apr 24, 2011
8,058
By that I mean, I need an IC that, when an input goes high (set), will make an output high until a different input goes high (the reset) or, if the set and reset were the same pin, i suppose that would work also anyone know anything that will work?
/QUOTE]

If set and reset can be on the same pin then can't you just use a well calibrated piece of wire?

I don't think MrChips is being a nit for pointing out how to MAKE a flip flop from gates that may be left overs (and thus free) in some design.

If I came to the end of the design and just needed ONE flip flop something like a NL17SZ74 single D F/F IC would probably be cheaper and smaller (and certainly fewer parts) then a discrete transistor version.
 

MrChips

Joined Oct 2, 2009
22,113
I don't think MrChips is being a nit for pointing out how to MAKE a flip flop from gates that may be left overs (and thus free) in some design.
No offense. What crutschow was saying is that he (crustchow) was going to nit-pic about definition. The terms used are bistable (two-state device) and astable (oscillator) - (not to be confused with a monostable and a horse stable). An R-S flip-flop is a bistable device. A flip-flop is usually a clocked bistable but does not have to be clocked. A D-latch is a different beast - a clocked transparent D-register. Still confused?
 
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crutschow

Joined Mar 14, 2008
25,690
.................
or, if the set and reset were the same pin, i suppose that would work also
anyone know anything that will work?
You can do that with a flip-flop by triggering the clock input. If you connect the inverted (not) output of the FF to the D input of a D FF, or connect the JK inputs to a logic high on a JK FF, their outputs will toggle between states for each clock pulse input.
 

Thread Starter

magnet18

Joined Dec 22, 2010
1,227
Alright, thanks for the advice guys :)
Hopefully I'll get a simple schematic up tomorrow for approval to make sure I know what I'm doing :)
 

Thread Starter

magnet18

Joined Dec 22, 2010
1,227
Will this work?
will it work if I have a diode right at the output of the 4017 that feeds the reset?
[EDIT]
See the second attachment
 

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Thread Starter

magnet18

Joined Dec 22, 2010
1,227
the only reason I could see for that not working is if holding the clock at gnd while triggering set and reset is unacceptable
Will it work?
 
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