Schmitt Trigger IC

Hello,
I want to recommend me a Schmitt Trigger IC for control the voltage level. For example if input voltage was lower than 4V and output be high and vice-versa also can detect changes in mV level with adjustable voltage level.

And have these specifications:

  1. 5V Single supply
  2. a few nano Secs Response time
  3. low noise

Hello,
I want to recommend me a Schmitt Trigger IC for control the voltage level. For example if input voltage was lower than 4V and output be high and vice-versa also can detect changes in mV level with adjustable voltage level.

And have these specifications:

  1. 5V Single supply
  2. a few nano Secs Response time
  3. low noise

A schmidt is a digital device - it’s output will only ever be at ( or close to ) Vss or Vdd.

And it’s (fixed) input thresholds are typically ( but not accurately) at 0.3 Vdd ( LOW) and 0.7 V Vdd ( High ).

The 74HCT14 is a common schmidt hex invertor.

A comparator ( eg a LM393) may be a better bet - but it will only deal with inputs up Vcc - 1.5v, and it’s response is a few uS. nS response requires something rather more exotic. Does it really have to be that quick?

A suitable divider chain would get your 4v threshold nto the working range.

Allan

allanhurst:
A schmidt is a digital device - it’s output will only ever be at ( or close to ) Vss or Vdd.

And it’s (fixed) input thresholds are typically ( but not accurately) at 0.3 Vdd ( LOW) and 0.7 V Vdd ( High ).

The 74HCT14 is a common schmidt hex invertor.

A comparator ( eg a LM393) may be a better bet - but it will only deal with inputs up Vcc - 1.5v, and it’s response is a few uS. nS response requires something rather more exotic. Does it really have to be that quick?

A suitable divider chain would get your 4v threshold nto the working range.

Allan

I’m using PIC12F1822 ADC for handling changes is voltage level. One of forum members told me the full conversion of this 10Bit ADC take 11.5 uS, and recommend me to use a Schmitt Trigger. I just need a component can sense changes voltage level in mV with fast response.
My reference voltage is 4V, how can I use LM393 When voltage level is lower than 4V?

If you want the trip point to be adjustable, you need to make your own using a comparator.

Why not just read the ADC continuously and compare it with your threshold in software?

Allan

@navab1362, do not cross-post. Threads merged.

jremington’s circuit won’t work with a LM393.

1/ if comparing about 4v as you say this is outside it’s input common mode range. Suggest cut the volts down to 2v with 2 equal (10k?) resistors.

2/ the LM393 has an open-collector output - so you need a pullup to +5 - say 4k7.

Allan

navab1362:
2) a few nano Secs Response time

That's going to mean a very high speed comparator I think. Response time depends on
the degree of overdrive, so with signals of a few mV you'll never get that speed of response
without first amplifying. Perhaps you need to think of a high frequency differential
amp followed by a hysteresis stage for mV level signals.

  1. low noise

Huh? How can a hysteresis device be low noise? Do you mean low voltage offset or low jitter
or something like that?

Some electronics is in the class of ' pretty straightforward - prototype it on a breadboard' .
Using a LM393 with a response time of a few uS is in this class.

Some is in the 'this needs very careful design and a clever PCB layout to work at all' class .
Eg most RF stuff and offline switchmode psus are here, and so is your mV overdrive nS response comparator.

Allan

Spreading the problems for a single project across several threads is never wise.

OP wants to detect a change in voltage of a TSL252R (7us rise time) light sensor for a ballistic speed gate.

Leo..

Well if its 7us risetime, the ns response time isn't possible is it?

An LM339 will do the job.

1/

I didn't read the other threads, so it's been a wild goose chasse.

OP -by opening several threads you had to wait longer for a definitive answer, and have confused and annoyed those of us trying to help you.

2/ A LM339 is a quad comparator - you don't need 4 . Use a LM393 dual comparator, but note my comments in reply #7

Allan