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Schmitt trigger design 0.25u

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inverting schmitt trigger calculation

Hi all,

Can anyone please help in designing cmos schmitt trigger circuit....VIL = 0.65v and VIH = 1.1v ..

I want the equations to design the same ..attached is the circuit which drives 5pf load..

Thanks in advance..

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equation for trigger schmitt

Equations is far from reality especially for 0.25u. Turn sizes of the inverter MOSFETs for trip point in the middle of Vil and Vih and for desired delays. Than to get Vol and Vih turn sizes of MOSFETs in positive feeback. Their are turned independently so it's easy to make.
If ur schmitt isn't driven from the PAD or any strong driver than to drive load 5pF it's better to add two inverter after with step-by-step increased sizes.
Good luck

Some reference regarding optimum tapered buffer are attached
 

schmitt trigger equation

Hi DenisMark,

Thanks a lot for the help.

I am able to drive the load without any issues and am using 2 inverters back to back for driving it.

I am following baker's approach but this is not solving the problem ..still im finding it difficult to make the circuit to operate on required vih and vil . is there any other approach to solve this ?

Thanks
 

3 inverter schmitt trigger design

I don't take what is the problem with vih and vil. Please explain more details about ur constrains and goals.
 

1.8v schmitt trigger cmos

The vil and vih range has to be 0.63mv to 1.1v but evan if i vary the widths of all the transistors in the schmitt trigger im stuck at vil 1.9e-14 and vih at 1.7 the schmitt trigger is driving few of the circuits ...please find the attachment which explains more about this ..this is basically a io buffer
 

schmitt-trigger fall time

0.63mv - ????????
vil 1.9e-1 - ???????
vary the widths of all the transistors - ???
What Vthp and Vthn for ur process? What hysteresis do u need? Do u make corner simulations?
Make the problem more clear.
 

inverter trippoint dc sim

yes i have to simulate for all possible corners ....

the vthn=0.46 and vthp=0.4093 for the nominal condition. i need hysteresis in between 0.7 to 1.1v with frequency of 10mhz and supply voltage of 1.8v .

hope this data is enough ...please let me know how to proceed
 

vol voh hysteresis schmitt trigger

Let begin from start.
Trip point for inverter are set to 0.9V.
"i need hysteresis in between 0.7 to 1.1v" is wrong answer, usually for 5V and 3,3V I/O it have value of 300mV. If it isn't constraint, let assume than Vhys=100mV. So Vih=0.95V and Vil=0.85V for typical corner. Turn the schmitt ckt for this values of Vih, Vil.
Because Vhys is small, the result sizes of MOSFET in inverter will be more than ones of positive feedback MOSFETs (10 time for e.g.).
Check corners that trip points of schmitt ckt are in the range of 0,7..1,1V.
 

calculate vih vil

as per the spec the vihmax = 1.17 and vil = 0.63v hence im trying to minimize it to 0.7 and 1.1 for the input clk voltage of 1.8 and core level voltage of 1.5v
 

what is schmitt trigger,give its working

U must to understand this means that real values of Vih and Vil must be in range Vilmin..Vihmax (0.63..1.17V). And u need to provide some hysteresis Hhys=Vihreal-Vilreal. U don't need to set Vilreal=Vilmin and Vihreal=Vihmax.
There is no problem to make io buffer according specification. I hope u determine Vil and Vih value though dc sweep analisys, not tran. Is it true?
 

schmitt trigger 100mv hysteresis

im running the simulations in transient analysis

i didnt understand how to calculate what you were asking could you please elaborate on the same.
 

schmit feedback with mosfet

:) Delay of logic gates gives u error in measured Vih and Vil values. Error is decresed when input slope is icreased (long rise/fall times). To eliminate this make dc sweep from 0 to 1,8V and determine where output transit from e.g. Voh to Vol (inverter), here u find Vih. Than make dc sweep from 1,8V to 0V, Vol->Voh, here Vil. It's easy and quickly. Refer for simulator help how to make dc sweep analisys.
Never simulate threshold values though tran analisys.
 

transistor schmitt trigger

yes i am doing the calculation in the same way and i have a tool to calculate the vil and vih which is showing vil 0.1 and vih 1.77v ..will the inverter included for reset signal before schmitt trigger give rise to any issue .

could you please provide the equations to calculate the w/l of schmitt trigger sck ?

Added after 3 hours 41 minutes:

hysteresis is 400mv max and 100mv min .
 

schmitt trigger cmos trip point equation

vil=0.1V? Do u sure? Mistake?
Equations? Do u see schmitt.zip sent by me early?
W/L ratio depends from output capacitance (there must be existed the delays and rise/fall time constraints for ur i/o buffer). Also W1/L1 for schmitt inverter more lager than W2/L2 for mos in positive feedback. To make Vhys=100mV it's requred that W1/L1>10*W2/L2 approximately.
So L1 - min., W1 as needed, if necessary increase L2.
Avalable equations are simple and gives you unaccuracy results any way. Try to find relation though simulation.
This task isn't difficult. Really there are more complex problems. Try to read books about simple inverter (keywords trip point, noise margin, delays, rise/fall time, optimum sizing inverters chain). Than read this book "Basic ESD and I/O Design" by Sanjay Dabral, Timothy Maloney.
 

how to calculate schmitt trigger

yes it was a mistake from my side, i am fresher for the design henceforth im asking you questions. Evan though it seems silly for many its kinda difficult for me .

Again Thanks a lot DenisMark, i will design and simulate. If i get in to unknown problem i will bug you again :)
 

schmidt trigger simulation

Thank DenisMark!
 

Hello there,
DenisMark could you please send this "schmitt.zip" to me to, or perhaps cater could send it to me. My problem with this circuit is the 2 transistors that are close to the middle point between the input and the output. How to size them, they doesn't seems to affect threshold values, but only the delay and current consumptions, so I should use the minimum size for them, am I right ?
 
Re: schmit feedback with mosfet

Dear DenisMark,

The Vih is the value of input when the output is Voh??
I am novice,don't know how to determine the Vil and Vih from the dc sweep.
 

In your circuit M9 and M10 are both drawn as NMOS which isn't correct.

Keith
 

Dear all,

are these mos both in saturation region???
 

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