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Go beyond the datasheet, Part 2: Understand the considerations

10/11/2010 03:44 PM EDT
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Bhola_#1
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re: Go beyond the datasheet, Part 2: Understand the considerations
Bhola_#1   10/30/2010 5:05:02 AM
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Good point. Another thing to notice is Absolute max rating on datasheets. Many a times, we misunderstand this section. Max rating doesnot guarantee performance for the device but tells that device may be damaged if exceeded this value.

nGENEr
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re: Go beyond the datasheet, Part 2: Understand the considerations
nGENEr   10/16/2010 8:34:29 PM
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Yes, you make good points also. There are a few advantages to a CMOS part. First, each new technology node is typically faster, so exceeding the clock speed should be transparant to a new die. But, then there is always the issue of fixing a bug and having it affect you. I've had that happen to me on occasion. But generally was an easy fix on my board. Second, we generally don't take an old device to a new technology node and keep the same part number. Lastly, your product life cycle is probably much shorter than our life cycle. And, if it isn't, then it may not be wise to use it out of spec. One additional point. A good way of using the information in the paper is for creating prototype systems and early production when the device isn't quite good enough for the application. But, with time you know you can better optimize the code and get it within spec. This gives you a short term path until the real optimized solution can be realized. Hope this makes sense.

nGENEr
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re: Go beyond the datasheet, Part 2: Understand the considerations
nGENEr   10/16/2010 8:25:57 PM
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You are correct. That is why is says in the introductin that using the device outside of the data sheet voids the warrantee. But, depending on the application, how far outside of the spec you want to run and which parameters you are exceeding, there may never be an issue. For example, driving the clock below the minimum of the data sheet should always be possible. Just the same clocking above the maximum of the data sheet should also be fine given you understand that you may be reducing the life of the product, or you may need to reduce the temperature range of operation. Remember we're aren't suggesting using a new feature, but just simple extensions to the specification. For a military product, I would never do this unless I was prepared to either guarantee the device my self or work with the vendor to give me a special part number for my application (along with the special part number, a data sheet and warrantee for the new spec. You make one other good point. Once you go beyond the data sheet, our applications engineers can't support you. But, once again this may not be a huge issue to you. And, if it is, stick to the data sheet.

Sensorguy_0623
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re: Go beyond the datasheet, Part 2: Understand the considerations
Sensorguy_0623   10/15/2010 4:00:14 PM
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Very enlightening information on the ability to increase clock speeds. One level of concern that I would have about depending on the going beyond specs, is what happens in the case of a die change. You could be in a position where the product works fine with lots of margin until a die shrink or similar change happens. Now, you need to ship product and can't get the old parts. I took over an ECL base product years ago where a needle generator was designed in. The product had been in production for 3 years. One day, everything in production was failing. The only fix available was to patch in a short piece of coax to obtain the required delay. You have some very good points, but go in with your eyes wide open and make sure that you have margin.

_hm
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re: Go beyond the datasheet, Part 2: Understand the considerations
_hm   10/12/2010 9:53:48 AM
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Some time we have encountered and employed hidden features of IC for test and debug purpose. However, going beyond datasheet is very high risk and it is very difficult to get approval from manufacturer or you supervisor. I may like to mention one example below. I was designing Hotlink for US DoD project. The earlier version was 160Mbps, Hotlink I working on 5Vdc. In new design I was employing Xilinx FPGA and main working voltage was 3.3Vdc. I wanted to employ Hotlink II IC which was 3.3Vdc and had many other advantages. However, Hotlink II was not characterised to work at 160 mbps. I wrote to Cypress Semiconductor for help. But since our temperature range was -55 C to 71 C and it was military application, they never were able to say yes to this application even though IC did worked for 160 mbps. I talked to other designers in our team but to no avail. Eventually, I had to use only Hotlink I IC.

patrick.mannion
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re: Go beyond the datasheet, Part 2: Understand the considerations
patrick.mannion   10/11/2010 4:18:40 PM
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Here in Part 2, Gene and Ivan elaborate on what you need to consider when going beyond the datasheet. Kudos to them for putting the guidelines together. What's been your experience of 'going beyond'?

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