WEBENCH Filter Designer

Hi, my name is bobby baker

And I work for the WEBENCH filter team

I'm here to talk to you

about the WEBENCH analog filter designer

In all analog systems you'll have a filter

that will appear someplace one place or another

For instance in data acquisition systems

they have the anti-alias filter

and the anti-alias filter is

actually a low pass filter

You would have a band pass filter

if you're doing under-sampling activities

in your system

Or if you want to get rid of 50 or 60Hz

or even the switching noise

from your power supply

you would use a band-stop filter

or typically called a notch filter

So I'm going to talk to you

about the WEBENCH filter

Active filter designer from TI

we took the filter pro from TI

and combine that with the active filter designer

from national semiconductor

And we took those two

and combine the software

and took the best of both

And came up with an optimum filter solution

We used the formulas and the intent verbatim

as we went forward

So how did we do this

We came out with a filter program

that would easily be implemented

you know

for you at your desk on the web

You get into this filter program you run

You figure out how to

select the kind of filter you want

And you then design it

And then you take a while to analyze it

So it's very easy 3 steps

Select, design and analyze

So enough talk right now

Let's get down to the software

and take a look at it

Up here I have the the cover page

for the filter designer

The way you get to that is

you type in ti.com/WEBENCHfilters

And here we are right here

And this is what will appear

And here you can actually

select the low pass or the high pass

band pass,etc filter here

But also there's a little tutorial

It will help you go forward

But we're not get a mess around with that

We're going to go forward

And we're going to just start

our design as low pass filter

And here we go

OK so now we're into the filter program

And again this shows up

the low pass,high pass, band pass

types show up

But I'm choosing not to change that

I'm sticking with low pass

And moving down here

I have the attenuation selection and stop

and selection in the power supply selection

But let's just let this go and

I'm going to design a low pass filter

for a sensor system

And I know that sensors are at low frequency

And I know I want to

get rid of a lot of noises

in the higher frequencies

as long as much as I can get rid of

so let's enter change

Instead of making the cut-off frequency 1000Hz

I'm going to make the cutoff frequency 10Hz

And that's right here

And then I'm moving down

and I want the stop-band frequency

which by the way happens to be right here

making the stop-band frequency 50Hz

And let me get rid of two zeros

So my filter is going to have

a cutoff frequency of 10Hz and down to 50Hz

It'll take 45dB to get down to 50Hz

So let's see if go with this

I also would like a single supply

And I would like to design

it with a 5V supply

So I'm happy with this design

And let me go forward

and start the filter design

Now i'm still in the process

of selecting my filter

When I go to the next page

And in the next page you'll see six panels

One is the optimizer

the second is changing the inputs

I can change the inputs

that I just put into the previous screen

And I can go back

and make some more changes here

and with a recalculate

Or I can refine these results

by changing the order of the filter,etc

And you can play with that

Down here in the bottom

there is an advanced charting panel

and solutions panel in the chart

The advanced charting panel

is actually has all of these solutions

that are in in bubble forms

so you can change the x axis and the y axis

according to the filter order

Let's just try that

And you'll get something that looks like that

Let me change it back to attenuation

And I get something like that

That's changing the y axis

Or you can change the bubbles to zero

and on the maximum Q

which is very interesting

When I pop on a bubble that I like

that solution shows up

here It pops into view

if I pop on this bubble I like

It's pops into view again

OK so here I have my solutions

Notice you have the

in this graph you have the color, the order

the max Q attenuation etc

You can go through that

The color is really interesting

because when I look at this black

and yellow and magenta

I go over to these charts

and I want to look at the settling time

I'm going to zoom in and here

And notice that the black line is here

That is actually your butterworth solution

And so it doesn't settle very well

And the magenta line is

the linear phase at 0.5°, etc

So that's really interesting

using the chart to finally

zero in on your circuit

And another place that I'm going to look in

is the optimizer

And I'd like to play with this one

This is set for three

which is the default setting

meaning the lowest cost

if I change it to two

I'll get the lowest settling time

And that filter will show up

at the top of the solution here

And it happens to be a Bessel

I'm not surprised the Bessel

is a pretty good settling kind of filter

And if I want to change it

to the the lowest pass band ripple

I'll flip it to here

And the butterworth is the one

that is it behaves the best in the passband

I'm going to select that

because I like that kind of behavior

So now I move past the select phase

Now i'm going to move into

the design phase with this program

And in this program you'll have

in the center you'll have

the circuit diagrams in the center

And then along the left

you'll be able to make some more selections

And wholly and really fix your design

On the top you have the description

of each of the filters underneath it

And underneath there

we have the bill of materials

for each of the filter

for each of the filter

So let's see let's go along this left column

And I want to stop here

I can change my Op-amp

and we're going to come back

and do that in just a second

I can also change the filter topology specification

by changing,let's say, to a multiple feedback

instead of the sallen key

I like that choice

And I say recalculate

or update, I guess

And it goes through that

and you'll notice that

a multiple feedback circuit

will appear on the screen

there it is

And here is the VCM which is halfway

between the supply and ground

to help it work

in a single supply environment

Moving down this left column again

I can tweak the design

by changing it from a butterworth

to something else at this point

Or I can change the order

of my filter which means that

this would fall off much faster

And every time I make those changes

I need to update it

I am going to select another amplifier

And let's see what I'm

it will give me

I'm looking for the OPA2244

and there is

And that has been plugged in

And from there I am now

going to move into the analysis state

So I finished my design

I'm happy with the design

And I'm going to in the analysis stage

In this stage, first of all

this system once I pop into this page

it immediately will simulate

the closed loop frequency response

And you'll notice here that

the cut-off frequency is 10kHz

like we had said it should be

And it falls off

as a fourth order filter would fall off

And here's a phase response

sitting right here

I can choose to do other simulations

I can choose for the

sine wave simulation response

Or I can choose for a step response

In each instance I have the ability

to change the input signal

In this case it's the high and the low

the step response

the delay and the rise and the fall time

in the pulse width

And I can do those kind of variations

If I run this step response

I'll come up with this kind of response here

And here she comes

there you go

nice step response there

It's a better worth it looks good

I'm not crazy about that

I'd like to just see this, the output

And I'm going to delete the input signal here

and I did that through

the wave form controls up here

And now I just have the output signal here

So I'm happy with this

And I'm going to print a design report

The design report comes up in a PDF format

And you can say this to your computer

Or you can send it to your neighbors etc etc

This is what the design report looks like

And there is your figure

your circuit diagram

followed by the bill of materials

You'll notice that these capacitors

and these capacitors and resistors

have manufacturers

They are real

and you can order them

At this point easily

And then the design inputs are listed right here

that we went through

and then one at a time

it goes through each state

and explains what the Q of that stage was

on the topology

and which stage number and you know

cut-off frequency,etc

All of that information is there

This concludes our tour

through the WEBENCH filter designer

As you can see we went through

And we did a selection phase

And we went and designed your filter

And then we went into an analysis stage

And finally we ended up with the filter

in just a minute

If you want to get to use this tool

please plug in at ti.com/webenchfilters

Hi, my name is bobby baker

And I work for the WEBENCH filter team

I'm here to talk to you

about the WEBENCH analog filter designer

In all analog systems you'll have a filter

that will appear someplace one place or another

For instance in data acquisition systems

they have the anti-alias filter

and the anti-alias filter is

actually a low pass filter

You would have a band pass filter

if you're doing under-sampling activities

in your system

Or if you want to get rid of 50 or 60Hz

or even the switching noise

from your power supply

you would use a band-stop filter

or typically called a notch filter

So I'm going to talk to you

about the WEBENCH filter

Active filter designer from TI

we took the filter pro from TI

and combine that with the active filter designer

from national semiconductor

And we took those two

and combine the software

and took the best of both

And came up with an optimum filter solution

We used the formulas and the intent verbatim

as we went forward

So how did we do this

We came out with a filter program

that would easily be implemented

you know

for you at your desk on the web

You get into this filter program you run

You figure out how to

select the kind of filter you want

And you then design it

And then you take a while to analyze it

So it's very easy 3 steps

Select, design and analyze

So enough talk right now

Let's get down to the software

and take a look at it

Up here I have the the cover page

for the filter designer

The way you get to that is

you type in ti.com/WEBENCHfilters

And here we are right here

And this is what will appear

And here you can actually

select the low pass or the high pass

band pass,etc filter here

But also there's a little tutorial

It will help you go forward

But we're not get a mess around with that

We're going to go forward

And we're going to just start

our design as low pass filter

And here we go

OK so now we're into the filter program

And again this shows up

the low pass,high pass, band pass

types show up

But I'm choosing not to change that

I'm sticking with low pass

And moving down here

I have the attenuation selection and stop

and selection in the power supply selection

But let's just let this go and

I'm going to design a low pass filter

for a sensor system

And I know that sensors are at low frequency

And I know I want to

get rid of a lot of noises

in the higher frequencies

as long as much as I can get rid of

so let's enter change

Instead of making the cut-off frequency 1000Hz

I'm going to make the cutoff frequency 10Hz

And that's right here

And then I'm moving down

and I want the stop-band frequency

which by the way happens to be right here

making the stop-band frequency 50Hz

And let me get rid of two zeros

So my filter is going to have

a cutoff frequency of 10Hz and down to 50Hz

It'll take 45dB to get down to 50Hz

So let's see if go with this

I also would like a single supply

And I would like to design

it with a 5V supply

So I'm happy with this design

And let me go forward

and start the filter design

Now i'm still in the process

of selecting my filter

When I go to the next page

And in the next page you'll see six panels

One is the optimizer

the second is changing the inputs

I can change the inputs

that I just put into the previous screen

And I can go back

and make some more changes here

and with a recalculate

Or I can refine these results

by changing the order of the filter,etc

And you can play with that

Down here in the bottom

there is an advanced charting panel

and solutions panel in the chart

The advanced charting panel

is actually has all of these solutions

that are in in bubble forms

so you can change the x axis and the y axis

according to the filter order

Let's just try that

And you'll get something that looks like that

Let me change it back to attenuation

And I get something like that

That's changing the y axis

Or you can change the bubbles to zero

and on the maximum Q

which is very interesting

When I pop on a bubble that I like

that solution shows up

here It pops into view

if I pop on this bubble I like

It's pops into view again

OK so here I have my solutions

Notice you have the

in this graph you have the color, the order

the max Q attenuation etc

You can go through that

The color is really interesting

because when I look at this black

and yellow and magenta

I go over to these charts

and I want to look at the settling time

I'm going to zoom in and here

And notice that the black line is here

That is actually your butterworth solution

And so it doesn't settle very well

And the magenta line is

the linear phase at 0.5°, etc

So that's really interesting

using the chart to finally

zero in on your circuit

And another place that I'm going to look in

is the optimizer

And I'd like to play with this one

This is set for three

which is the default setting

meaning the lowest cost

if I change it to two

I'll get the lowest settling time

And that filter will show up

at the top of the solution here

And it happens to be a Bessel

I'm not surprised the Bessel

is a pretty good settling kind of filter

And if I want to change it

to the the lowest pass band ripple

I'll flip it to here

And the butterworth is the one

that is it behaves the best in the passband

I'm going to select that

because I like that kind of behavior

So now I move past the select phase

Now i'm going to move into

the design phase with this program

And in this program you'll have

in the center you'll have

the circuit diagrams in the center

And then along the left

you'll be able to make some more selections

And wholly and really fix your design

On the top you have the description

of each of the filters underneath it

And underneath there

we have the bill of materials

for each of the filter

for each of the filter

So let's see let's go along this left column

And I want to stop here

I can change my Op-amp

and we're going to come back

and do that in just a second

I can also change the filter topology specification

by changing,let's say, to a multiple feedback

instead of the sallen key

I like that choice

And I say recalculate

or update, I guess

And it goes through that

and you'll notice that

a multiple feedback circuit

will appear on the screen

there it is

And here is the VCM which is halfway

between the supply and ground

to help it work

in a single supply environment

Moving down this left column again

I can tweak the design

by changing it from a butterworth

to something else at this point

Or I can change the order

of my filter which means that

this would fall off much faster

And every time I make those changes

I need to update it

I am going to select another amplifier

And let's see what I'm

it will give me

I'm looking for the OPA2244

and there is

And that has been plugged in

And from there I am now

going to move into the analysis state

So I finished my design

I'm happy with the design

And I'm going to in the analysis stage

In this stage, first of all

this system once I pop into this page

it immediately will simulate

the closed loop frequency response

And you'll notice here that

the cut-off frequency is 10kHz

like we had said it should be

And it falls off

as a fourth order filter would fall off

And here's a phase response

sitting right here

I can choose to do other simulations

I can choose for the

sine wave simulation response

Or I can choose for a step response

In each instance I have the ability

to change the input signal

In this case it's the high and the low

the step response

the delay and the rise and the fall time

in the pulse width

And I can do those kind of variations

If I run this step response

I'll come up with this kind of response here

And here she comes

there you go

nice step response there

It's a better worth it looks good

I'm not crazy about that

I'd like to just see this, the output

And I'm going to delete the input signal here

and I did that through

the wave form controls up here

And now I just have the output signal here

So I'm happy with this

And I'm going to print a design report

The design report comes up in a PDF format

And you can say this to your computer

Or you can send it to your neighbors etc etc

This is what the design report looks like

And there is your figure

your circuit diagram

followed by the bill of materials

You'll notice that these capacitors

and these capacitors and resistors

have manufacturers

They are real

and you can order them

At this point easily

And then the design inputs are listed right here

that we went through

and then one at a time

it goes through each state

and explains what the Q of that stage was

on the topology

and which stage number and you know

cut-off frequency,etc

All of that information is there

This concludes our tour

through the WEBENCH filter designer

As you can see we went through

And we did a selection phase

And we went and designed your filter

And then we went into an analysis stage

And finally we ended up with the filter

in just a minute

If you want to get to use this tool

please plug in at ti.com/webenchfilters