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Kerry Lacanette

Integrating Time

Kerry Lacanette
Brad Albing
Brad Albing
3/20/2013 7:02:37 PM
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Re: AFE data sheets vs specs vs use
Kerry - the point you were making righjt at the end - cost - yep. I went thru those problems at Intersil when selling to customers. We would have component X that the customer wanted and really liked the specs for  - mostly. But the wanted to know if the device (e.g.) work down to -50C instead of merely -40C. And we knew it would, just because we knew how the silicon performed in general. But we never tested it at -50C since only 1 customer in 100k needed that spec - so we couldn't guarentee (by virtue of testing during manufacturing) that spec. Or we could if wwe wanted to triple the price.

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Brad Albing
Brad Albing
3/20/2013 6:51:36 PM
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Re: Any real world examples?
Any chance we could see schematics of any portion of the design?

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jkvasan
jkvasan
2/27/2013 6:53:42 AM
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Newbie
Re: Any real world examples?
Why not?

I designed a 12 lead ECG amplifier. Though it is called a 12 lead, 10 signals were acquired, amplified, filtered, processed and further amplified to scale up to ADC range. In total, there were 8 processed analog signals. A SPI 12 bit ADC with 8 channel inputs was used to convert these into Digital data to be fed to a MCU.

The signal conditioning and amplifying used 14 analog ics, around 100 resistors, 40 capacitors, protective diodes, ferrite beads apart from a DC DC converter to generate positive and negative voltages. The PCB size was approximately 140 mm by 120 mm.

Though this worked, we wanted something better, faster and smaller. When an AFE from TI was introduced, we jumped at it. It was a single SMD IC occupying very small space and replaced all those components including the ADC excluding the protective diodes and ferrite beads. Added to this, we got 24 bit resolution.

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Kerry Lacanette
Kerry Lacanette
2/18/2013 12:52:30 PM
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Re: AFE data sheets vs specs vs use
It seems to me that the "embedded" specs work best when the integrated component has a single function and there's little or no deviation allowed from the target function. Ideally, if the component has enough flexibility to be used in other applications, then the developer needs to assume that someone will want to use it in those other applications. It's best if the specs are comprehensive enough to allow the designer to predict the performance in "non-target" applications.

And yes, there have been cases where a "hidden" spec was added to a data sheet after an IC had been on the market for a while; in those cases it would have been easier for everyone if the specs for the individual blocks had been listed on the data sheet from the beginning.

Every case is different, but in general IC developers do think about non-target applications where their products might be used, and have to make a decision about whether to publish the detailed specifications that would help in using the product in those applications. Cost is often a factor, as the additional specs may require more testing. So a chip that's aimed at a very low-cost, high-volume application may not meet its cost goals if the testing is done to guarantee all of those "internal" specs that would make it ideal for other designs.

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Kerry Lacanette
Kerry Lacanette
2/18/2013 12:51:07 PM
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Re: Any real world examples?
That's an excellent idea. It would be interesting to see a system designer's experiences with making the choice between an integrated design and a less-integrated one.

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Kerry Lacanette
Kerry Lacanette
2/18/2013 12:50:23 PM
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Re: Integrating time at cost.

Thanks for the comment. I agree with you that as the level of integration increases, there are a lot of potential problems that can hinder success if they're not handled properly.


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eafpres1
eafpres1
2/16/2013 3:31:33 PM
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Blogger
AFE data sheets vs specs vs use
Hi Kerry--there has been some other discussion here about the specs associated with integrated parts.  Your point about "embedded" specs is good-if the input and output specs meet your needs, you can treat some of the block as a black box.  Some conerns have been expressed that there are subtleties that can get buried in the integrated part.  Have you seen any issues were behavior related to either (a) behavior not specified by the integrated part data sheet (i.e. off spec use) or (b) lack of specs at the higher level casued designers headaches further downstream (like in full board test?)?

 

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karenfield
karenfield
2/16/2013 3:26:04 PM
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Newbie
Any real world examples?
Hi Kerry I'd love to see the details of any real world examples where the design using integrated analog, would be great to learn about the decisions and tradeoffs that the designer had to make. Would be a great roadmap for engineers as they evaluate this solution in their own designs.

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amrutah
amrutah
2/16/2013 12:57:59 PM
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Master
Integrating time at cost.

Kerry, Thanks for the post.

I have to agree to, "the right chip not only integrates circuit blocks, it also integrates time".  All the customer wants is a single chip solution so that he may not invest much time into debugging the system, all he has to do is check if that chip is not working or meeting the specifications and report it back to the vendor.  The component list and BOM of the customer reduces and the system debug time.

  But as the integration increases, one has to be critical about the die size and package, testing time/cost, EM, on-chip temperature variations and reliability...

 

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