Looking for product longevity advice (Roadmap) with integration of Linear Tech

I am looking to select a couple of data converters for an instrument I am designing. The company I work for has glacial product development life cycles so whatever I parts I pick need to be supported for the long haul (the previous generation of their products was designed in the '90s). I know that Analog Devices is buying Linear Tech which doesn't give me warm fuzzies about any part in either companies portfolio right at the minute.  Don't force me to go to TI for this now.

ADC 1: One channel, 18 bit, high DC precision, 100 to 250 KHz sample rate, differential inputs, and a SPI interface. A SAR is what I am looking for. The SAR we most recently used was the AD7691 and we found it's performance acceptable. However, I really don't want to base a new family of products on a part that might be obsolete in 3 years.

ADC2: One channel, 24 bit, high DC precision, ~10 Hz output rate, differential inputs, and a SPI interface.. This will just about have to be a delta-sigma part.

I am also looking for 16 bit voltage output DAC as well. SPI, +/-10V, 10 uS settling time or better. The AD5761R looks interesting, but again longevity is a key characteristic more so than cost.

Let me know if anybody has any insight into what Analog Devices is planning to do with their and Linear Tech's portfolio of parts.

  • 0
    •  Analog Employees 
    on Feb 9, 2017 12:10 AM

    Hi Phil,

       for ADC1 I can recommend to you one of the latest in the ADIs  SAR ADC portfolio, the AD4003 which I think fit the specification you've mentioned above.

       For ADC2 you can check the AD7789 or AD7791(on chip buffer). You may also try to have a parametric search in the ADI website, you can refer to the link http://www.analog.com/en/parametricsearch/11007#/p1746=16.6|1000000&p3062=1&p193=24&p4364=Sigma-Delta.

       Are you using these parts in a single  system or each has different application? If there would be a way we can grasp your application, we could help you find or filter some parts for specific application or  some circuit note or application notes for reference that are available.

    Regards,

    Jonathan

  • Thanks guys this is exactly the kind of feedback I am looking for. Nobody can guarantee long term, but it helps to know parts that are more likely to still be around in the future.

    These are all going on the same product. It is a force sensing instrument that will be used in several different applications. One is a four channel, higher precision, lower speed, static force sensing (load cell) application, the other is a single channel, medium precision, higher speed, dynamic force sensing (rotary torque) application. That is why the two different ADC requirements. I considered one of the quad channel parts for the static application and decided these are probably more likely to be obsoleted earlier than single channel parts are.

    One thing that TI did with their LDO portfolio that I really like is they have parts continuity for specific packages and pin assignments. If you buy a regulator in a specific package, they promise to keep releasing compatible new parts that will drop onto your existing PCB without revision.

    I don't know if Analog Devices does something like that with DACs or ADCs. If so I would be very interested in selecting a part in one of their standardized packages. I don't mind revising the firmware to accommodate new functionality, but it sucks to have to revise a PCB, just to move pin assignments around.

    Again, thanks for the input.

    Phil

  • 0
    •  Analog Employees 
    on Feb 9, 2017 11:25 PM

    Hi Phil,

    The AD7691 is part of a 10 pin SAR family that are pin and package compatible. You can see this in the parts table in the AD4003 datasheet (table 8). The most recent release in this 10 pin compatible family is the AD4003 which was released last Nov. So even though there is no risk of the AD7691 being obsoleted for a very long time you can always upgrade to the AD4000/3 family. In the next year we plan to release the rest of the products in the AD4000 family which will include lower throughput versions like the AD4011 (LFCSP package only) which is 500ksps. The only difference with these parts from the AD7691 is that they require a fixed 1.8V VDD. As long as you have the capability of adjusting the VDD supply to 1.8V then you can upgrade or change parts at a later date to the AD4000 family without respinning your PCB.

    Best Rgds,

    Alan

  • Philip,

      I'm in Central Apps at ADI, so I can't say specifically what the exact lifetime will be on any one part, but no one

    can.  Consider:  One part has ten customers, each one buys $100k/yr and one customers moves on to his

    next generation product so he stops buying.  Another part has ten customers;  one buys $910k/year and the

    other nine buy $10k/yr.   The big guy stops buying.  Third case:  A part has good volume, but it's on a very

    old fab line and the other parts on that line drop in volume so the fab gets shut down.  Fourth case:  A part

    requires an exotic process, so the semiconductor company uses an outside foundry for fab and the outside

    foundry gets out of the business.  (That's what happened to some of the Hittite parts after we bought them).

    So you can see there is no simply way to predict what the lifetime will be.  We have one op amp that is

    37 years old, and we have one part that was released five years ago that is gone.  But here are some

    general guidelines.

    --  Bits keep increasing, so 14-24 bit ADCs will be around longer than 8 or 10 bit ADCs.

    --  Go with singles and duals;  we see lower volume with 4 or 8 input ADCs.

    --  For higher speed, go with LVDS or JESD204 interface.

    --  People want smaller parts;  PDIPs are going away and parts with serial interfaces have smaller packages

       than parts w/ parallel interfaces.

    --  Ask the company.  Do not use "prediction" software that was developed by outsiders.

    Having been in the semiconductor industry for many years, I will say that I think ADI has one of the best

    obsolescent policies of any semiconductor company.  Let's say you use 1k/yr of a part.  We announce

    the part Not recommended for New design.  This can mean that we have a next generation part and it

    could be that we make the NRFND part for ten more years.  Usually the product page will tell you about

    the new part.  E.G. for the OP284:

    Search | Analog Devices 

    http://www.analog.com/en/products/amplifiers/operational-amplifiers/high-voltage-amplifiers-greaterthanequalto-12v/op284… 

    Then we change the status to LTB = Lifetime Buy.   You have one year to place orders and the following year

    to take delivery.  So you could give us an order for 12k parts, with 1k now, 1k in 12 months, and 10k in 23 months.

    As long as you store the parts properly, you have a 10 year supply.

    Sometimes we will sell the mask set, test tape, WIP and finished goods to Rochester Electronics: 

    www.rocelec.com

    They have 8 billion die from over 60 companies in their die bank.  They sell for 20-30 years.

    Another option:  Sometimes the commercial part is obsoleted, but the Mil (5962-xxxx) or Space level

    part is still made.  True, some of the space level parts are $500-$1,000 per part, but if you need one

    twenty years from now for a critical field replacement, that's available.

    In general, if a part is 10-15 years old, and you need 20 years of life, you probably want to go with

    parts that were released in the last 1-9? years??

    In addition to the AD4003, you could also look at the AD7989-5.

    For ADC2, look at AD7780 or AD7797 also.

    For the DAC, AD5761.

    This is my own personal opinion;  the data acquistion group may have further comments.

    Harry

  • I am going to go with the AD7691. It has better noise performance than the AD7989 and is already in our system. Since the AD7691 is one of the pin-for-pin compatible parts I am not as worried about future proofing the design, I will include provisions for 1.8V VDD to be safe (thanks for the suggestion).

    This question has been answered in my opinion.

    Well, except we totally ignored the Linear Tech parts. I guess you Analog Devices guys either don't know what is going to happen or have been told not to tell. Like I said, the 10 pin SAR pin-for-pin replacement family really helps with my decision making.

    Glad you guys are doing that.