ADC Model, Getting Started

[auk_ie]

Hi all

I'm trying to get back into electronics after a few years of neglect,
My design revolves around a hi speed adc operating at 1Ghz from Maxim.

So now I want to connect all the components together in PSpice. But
the problem is the vendor doesn't provide a model for this ADC. So I
guess I am forced to build a model of the ADC myself. I know this is a
next to impossible task in spice. But all I want is to model an ADC at
a behavioural level. I would like as many real worlds affects in the
model as possible, but I hear thats a hard thing to do, so I would be
happy with just a functional model of the ADC so I can proove my
circuit in concept. What would be good is to have a model that
accounts for the sample and hold, the conversion and the demultiplexed
PECL outputs.

I don't know where to start with this. I have looked at VHDL-AMS which
looks like that it can do the job. But I can't find a simulator in
which I can use my spice parts of the circuit and conect it up to the
AMS based ADC model. PSpice is great because you can simulate spice
models as well as vhdl/verilog parts. But not VHDL-AMS.

I also looked at Matlab and Simulink. I think its possible to model
such an ADC with these tools and then import the model back into
pspice. But I have no resources on how to do this.

I'm sure people have modelled an ADC in there designs before. Can
anybody point me in the right direction? Tools to use? Workarounds
etc.?

 

[Kevin Aylward]

auk_ie wrote:

Hi all

I'm trying to get back into electronics after a few years of neglect,
My design revolves around a hi speed adc operating at 1Ghz from Maxim.

So now I want to connect all the components together in PSpice.

Oh dear...

But
the problem is the vendor doesn't provide a model for this ADC. So I
guess I am forced to build a model of the ADC myself. I know this is a
next to impossible task in spice.

Pretty easy if one knows what one is doing

But all I want is to model an ADC at
a behavioural level. I would like as many real worlds affects in the
model as possible, but I hear thats a hard thing to do, so I would be
happy with just a functional model of the ADC so I can proove my
circuit in concept. What would be good is to have a model that
accounts for the sample and hold, the conversion and the demultiplexed
PECL outputs.

I don't know where to start with this. I have looked at VHDL-AMS which
looks like that it can do the job. But I can't find a simulator in
which I can use my spice parts of the circuit and conect it up to the
AMS based ADC model. PSpice is great because you can simulate spice
models as well as vhdl/verilog parts. But not VHDL-AMS.

I also looked at Matlab and Simulink. I think its possible to model
such an ADC with these tools and then import the model back into
pspice. But I have no resources on how to do this.

I'm sure people have modelled an ADC in there designs before. Can
anybody point me in the right direction? Tools to use? Workarounds
etc.?

Yes. I shall of course, force you to download my SuperSpice
(http://www.anasoft.co.uk
) demo in order for you to get your model.

It is an interesting post, as when I first looked at this issue myself,
I could not find any generic spice models that did this rather basic
function. It was a case of reinventing the wheel. The AD model I finally
came up with is an instantaneous successive approximation using simple
spice primatives.

Open the example 16Bit-AD-DA.sss, and press the blue "R" button to run
it. Move the test point to see the digital logic levels.

If you click on the adc and dac symbols the model text will show up in
the top left docked window. The models will run in any spice. The model
themselves are in AnalogDigitalLogic.lib. There are 4, 8 an 16 bit
versions of both ad and da. Have a go at decoding what the block diagram
of the technique is.

Kevin Aylward
salesEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Charles Edmondson]

auk_ie wrote:

Hi all

I'm trying to get back into electronics after a few years of neglect,
My design revolves around a hi speed adc operating at 1Ghz from Maxim.

So now I want to connect all the components together in PSpice. But
the problem is the vendor doesn't provide a model for this ADC. So I
guess I am forced to build a model of the ADC myself. I know this is a
next to impossible task in spice. But all I want is to model an ADC at
a behavioural level. I would like as many real worlds affects in the
model as possible, but I hear thats a hard thing to do, so I would be
happy with just a functional model of the ADC so I can proove my
circuit in concept. What would be good is to have a model that
accounts for the sample and hold, the conversion and the demultiplexed
PECL outputs.

I don't know where to start with this. I have looked at VHDL-AMS which
looks like that it can do the job. But I can't find a simulator in
which I can use my spice parts of the circuit and conect it up to the
AMS based ADC model. PSpice is great because you can simulate spice
models as well as vhdl/verilog parts. But not VHDL-AMS.

I also looked at Matlab and Simulink. I think its possible to model
such an ADC with these tools and then import the model back into
pspice. But I have no resources on how to do this.

I'm sure people have modelled an ADC in there designs before. Can
anybody point me in the right direction? Tools to use? Workarounds
etc.?
Look in the dataconv library, and you should see several ADCs listed

there. Place one and descend into it, and you will see what is
necessary to model an ADC in PSpice...

--
Charlie
--
Edmondson Engineering
Unique Solutions to Unusual Problems