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Maxim Integrated - Integration Nation
Dennis Feucht

ASICs vs. Semi-Discrete Design

Dennis Feucht
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CarlWH
CarlWH
7/15/2013 6:21:32 AM
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Re: it's a complex subject
Hi,

Sorry for the delay in answering but I have been out of office.

Scott, I understand the points you are making and you are correct in the companies like ADI will be involved in R&D for their products. However, these are standard parts, not in my view ASIC's. That said, companies like ADI, will design an ASIC for you, and they will have their business model, (like any company does), and if your design does not fit into this it will not happen with them. As standard parts are there to gain maximum volume, they will not always be optimum performance for your application, indeed many may be over specified for a design, hence the need for an ASIC.

Please do not get me wrong there are many designs where an ASIC does not make any sense what so ever, my point was you cannot generalise about when this is. We have done designs for less than 100 parts, as well as designs for millions.

My point about quality, was not just the quality of the device, (this is key to many markets irrespective of volume and there are many techniques used in testing devices, and the models available from the fabs nowadays are excellent), but it was about the subsystem it goes into. Let's consider medical, as it was mentioned, qualifying a medical product can (and does) take years. Any re-qualification, say due to a part change, is a big problem. So you have to decide how you mitigate this risk.

Cost is always the big question, and we have seen it is possible to get cost reductions for designs of what would be considered low volume. My point was it is relatively easy to determine if it is cost effective and should not be discounted as an option just because the volumes are "low". I have not defined low on purpose, as I do not think there is an absolute number for it.

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Bob @ JVD Inc.
Bob @ JVD Inc.
7/10/2013 8:38:17 PM
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Blogger
it's a complex subject
      Hi Scott.

We may be getting off topic here... the subject is ASIC vs "Semi-discrete design"

 

Your comment, " the imperfect human contribution is all over the place." is true whether the design is an Analog ASIC or a standard analog IC. There is lots of human involvement in both compared to digital.

 

Similarly you said "one could route the current through a metal line that is too narrow or has too few contacts/vias for the designed current. Here we can have an electro migration quality failure introduced during the design phase."  I fail to see how this applies to analog ASICs more than a standard analog product.  Looks like you are describing either a failure to adhere to design rules or improper processing in the fab.... Neither of which is more or less prevalent in analog ASICs.


Finally:
"When analog design becomes fully automated without much human involvement, then I would be open to the suggestion that making something 1000 times is just as high quality as making something 10 Million times." 

 

WOW! If this were to be true then heaven help those customers who have the nerve to design in any new analog IC...because the implication here is that the quality will be risky until the supplier makes 10 million units.

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Brad Albing
Brad Albing
7/7/2013 10:49:28 PM
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Re: It is a complex subject
Uh-oh - now we're getting the lawyers involved. With a lot of ICs, we often see the disclaimer stating that the manufacturer is not responsible for your screw-ups; so when you hurt someone, [they say] it's not their problem.

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Scott Elder
Scott Elder
7/5/2013 12:28:07 PM
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Re: It is a complex subject
Carl, I think another reason to consider an ASIC would be Liability.  This would apply for medical ASICs primarily.  So, Size-Liability-IP-Obsolescense.   

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goafrit2
goafrit2
7/4/2013 6:54:00 PM
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Master
Re: It is a complex subject
>>   It seems that once ones volume drops to a small amount, perhaps it makes more sense to simply be an aggregator.

In my office, our barometer is any order that is less than one million units, never consider a full ASIC. In this business, you need volume to make money in ASIC because it is very complex, expensive and difficult than the alternatives. 

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Scott Elder
Scott Elder
7/4/2013 4:05:11 PM
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Re: It is a complex subject
Hi Bob,

 I have to disagree with you on the issue of quality in low volume analog.  Simply because an analog design is manufactured on a high volume wafer line using high volume packaging and common design tools/models does not allow one to ignore the quality impact of a new circuit design.  If we were discussing digital design, I might agree.  In digital, human involvement is becoming less and less each year.  But in analog, the imperfect human contribution is all over the place.  Here are two examples of how a 100% qualified manufacturing flow can result in a lower quality analog IC.

 MOSFET current mirrors are found everywhere in an analog IC design.  And MOSFETs wear out as a function of the Vds and Vgs bias conditions as a result of hot carrier injection slowly destroying the drain-gate interface.  I don't think MOSFET models even capture this well-known nuance because no one would simulate a circuit for the time it would take to see a failure.  But I have seen several designs over my career where the designed Vds is too high and the device eventually fails.  The rate of failure is different for different wafer lots--it can be from minutes to years.

 In a similar vein, and using the current mirror example again, one could route the current through a metal line that is too narrow or has too few contacts/vias for the designed current.  Here we can have an electro migration quality failure introduced during the design phase.  And the failure rate will be a strong function of what was produced on the failed wafer lot (i.e. metal thickness for parts from the qualification lot was thicker than a later production lot).

 From my perspective, the more data one produces on a part, the higher the confidence level is for that part.  This is why many analog standard parts enjoy long lifetimes.  All of the bugs have been worked out over many hundreds of millions of installed and operating units in all types of environments.

 When analog design becomes fully automated without much human involvement, then I would be open to the suggestion that making something 1000 times is just as high quality as making something 10 Million times.  We are almost there with digital, but analog still has a way to go before the human factor is removed.

 

 

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Bob @ JVD Inc.
Bob @ JVD Inc.
7/4/2013 11:05:56 AM
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Blogger
Re: It is a complex subject
My 2 cents:

 

I agree with most of the commentary on this thread. That said, I think that quality is not a strong motivator for ASIC development. Scott's comment implies, although I hope I'm misinterpreting it, that a low volume ASIC will have inherently lower quality that a high volume standard product and that is just not the case.

Quality is conformance to a spec.  ASICs are run on the same processes or combinations of processes, as high volume standard products. They are designed with the same tools (Cadence, Synopsys, Spice). Fabs produce 10s and 100s of thousands of wafers on these processes. Unlike the 'old days' when wafer fab involved some 'black magic' to get it right, today's fabs have it nailed. A low volume ASIC wafer's quality (the manufacturing aspect of the wafer and this includes the design rules established by the fab upon which the design is engineered) is no different that of a high volume standard product.

So let's consider the design. Scott, you state that big companies, like LTC, ADI wouldn't put their 'best talent' on a low volume / low return on investment part. While this may be true, the implication is that lesser talent is what is available for lower volume applications. While I cannot speak for all Analog ASIC companies, I can speak for JVD, and that too is just not the case.  JVD has been in business for 31 years and while this may be hard to believe, the company has never had a single quality return...not one!

Referring to CarlWH's original comment, I think rather that number 5. 'Quality', that customers consider ASIC's for Reliability. Reducing component count, board simplification, etc. can offer a measurable improvement in reliability. It's rarely a chip that fails these days...it's things like solder joints.

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Scott Elder
Scott Elder
7/3/2013 9:59:09 PM
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Re: It is a complex subject
Thanks for your response.  If we limit the discussion to low volume ASICs--since high volume is by all measures essentially a standard product--I'm not sure the list is that long.

For example,

(1) Performance requirements - There is a lot of tough R&D done inside companies like ADI, LLTC, etc. to produce the absolute best performance parts available.  I would doubt they do this and then limit the sales to a proprietary 1000 unit/mo socket.  I think rather it is the other way around.  Highest performance and a company's best talent is found working on parts with the highest return on NRE.  Its not unreasonable to spend millions developing the next generation, best in class ADC, for example.  

(2) Cost reduction - I think it will always cost more at low volume to do an ASIC because the NRE ends up factoring into the total money spent over the life of the program.

(5) Quality - I think a part that sees 1 Million units per month volume experiences substantially more critical quality evaluation than a part that is made 1000 units per month.  By critical I don't mean necessarily the limits of a test, but rather the confidence level in the socket.  Low volume quality is based upon mathematical extrapolation.  High volume quality is based upon actually making multiple six-sigma size lots every month thereby generating real data to study.

But, the other three...

3.     Size

4.     Obsolescence

6.     IP protection



I can see where these would make sense.

 

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RedDerek
RedDerek
7/3/2013 11:58:23 AM
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Master
ASICs for other useage
When I was an apps engineer, there were a few customers that we created ASICs for. They paid nicely from what I heard. However, the focus of an app engineer working with a customer for a new product is to figure out what other applications the chip can be used for; at least in my opinion. This way more than one customer would be able to use the product. My last few semiconductor ideas were such that a design could be done once, and then, between a combination of packaging, bond wiring, and metal masking, many other products could be spun out. This is the best approach in my view - one design, multiple products.

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DaeJ
DaeJ
7/3/2013 9:58:38 AM
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Master
FPGA/ASIC vs Semi-Discrete component
It might be a differnet topics as adding to FPGA, but both of FPGA and ASIC has a integrated circuit. In my view, depending on project condition, either FPGA/ASIC, discrete semi-discrete component or combination might be carefully evaluated, as reviewing the design time and cost with man power and validtion cost.

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