CD4011BE static sensitivity

Discussion in 'General Electronics Chat' started by Rissy, Dec 14, 2015.

  1. Rissy

    Thread Starter Member

    Nov 23, 2015
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    Hey folks,

    I'm working on a project which uses Texas Instruments CD4011BE NAND IC's. I'm finding a lot of them are going into the bucket due to them not working properly. I've been designing a circuit for the past couple of months, and have finished prototyping each component area of the overall circuit, and everything has been going well. Now however, i'm tryinig to get the main logic brain of my circuit working and have found that out of about 22 NAND chips i've bought, only 2 actually work in my circuit. I need four in total to work the whole thing. I've ordered another 16 from a seller on Ebay and i'm waiting for delivery later this week.

    The two I have which work on one half of my circuit, i've moved between positions to the other half of the circuit, and have proven that they work wherever I put them. But as I say, these are TWO....of around 22! Out of the failing ones, I've resisted throwing about 10 of them straight into the bucket, and gone through the laborious exercise of testing them with a multi meter instead; testing each NAND gate in turn with all four permutations of input possible states. From this testing, I threw 4 away because I confirmed that, for whatever reason, one or more of the gates wasn't working properly. This left me with 6 (in addition to the 2 working ones) which tested fine with my multi meter testing, yet they still wont work with my circuit!? I'm most confused!!!??

    Has anyone else had a great amount of difficulty with these chips? Am I destroying them with static even though i'm gingerly handling them with kid gloves, touching only the back plastic body? (I've not got a static mat or wrist band, and with the two which i've got working, i've intentionally "man handled" them in between proof tests on my circuit, to see if I could intentionally damage them with my hands, but they keep on ticking no problem, so this leads me to suspect that all the others shouldn't be that sensitive either!?) I've been doing things like touching radiator piping etc in the house before touching the chips in an attempt to ground myself etc just to try and be as static free as possible. But as I stress, only 2 keep working fine. All the others refuse to work.

    any help/advice?
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    Never happened when we bought from a reputable distributor. You might have bought empty leadframes encapsulated in plastic.
     
  3. Rissy

    Thread Starter Member

    Nov 23, 2015
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    Like say, they seem to work with a multi meter, at least the remaining ones i've not found a fault with and thrown in the bucket. they work under test ,but once i plug them into my circuit, they don't, even though the two "good ones" do work in the exact same positions!?

    Maybe I ought to try buying them from RS or Farnell or somewhere....?

    I've bought some from Maplin. First, i bought three from them. only one worked. then, on Saturday, I bought another two. Neither worked!

    They weren't even storing them in anti-static bags or anything! Just lying in an empty drawer! I even commented to the guy, asking him if that's how they normally stored them. He just laughed and said yes.
     
  4. dl324

    Distinguished Member

    Mar 30, 2015
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    Given the amount of counterfeit product coming out of China these days, caution is advised. eBay Sellers dealing in counterfeit parts will soon learn that being shipped from China is a red flag and will start setting up local shipping; so buying from a reputable source is your best bet.

    CD4xxx ICs have static protection in them, but it's always best not to test it. I ground myself before handling them. I don't wear a grounding strap and only use my antistatic mat occasionally. But I don't do dumb things like walking across the carpet with a handful of static sensitive parts.

    If you're seeing a high failure rate and are using sane handling procedures, I'd suspect defective parts and ask for a refund.
     
  5. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Can you show your schematic? Are you sure you have the power supply properly decoupled and all unused gates connected to gnd or vcc?
     
  6. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Could be your circuit. Is the schematic a secret? Photos?

    ak
     
  7. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    A common misunderstanding is that a floating (non-connected) input is the same as a low-level input. It is not. All inputs must be connected to ground or supply voltages.
     
  8. Rissy

    Thread Starter Member

    Nov 23, 2015
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    I'm not sure what you mean by having the supply decoupled, but my circuit requires 8 2-input NAND gates, so ALL are being tied to a high 9 volts or a ground depending on the state of the input cycle (which changes according to the inputs driven)

    All the chips i've received are lazer etched with Texas Instruments markings on them. They don't appear to be unbranded or counterfeit....?
     
  9. Rissy

    Thread Starter Member

    Nov 23, 2015
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    Like I said. I don't believe my circuit to be the problem. My two good chips, as long as they are in a linked pair, they work in both positions. If you separate them from being a pair,, using them individually with another two random chips, then they don't work. My circuit (for which there are two halves, only joined by the power being fed into them) has been proven in both halves using the two good chips i have.
     
  10. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    I mean if you have at least one 100nF ceramic capacitor across each IC supply pins.

    Also what about the unused pins, do you have them connected somewhere?
     
  11. Rissy

    Thread Starter Member

    Nov 23, 2015
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    All pins are being used.

    I'm feeding them using a 7809 MOSFET, which has a diode input voltage separated 0.33uF capacitor on the input and a 0.1uF capacitor on the output.

    like this:
     
  12. dl324

    Distinguished Member

    Mar 30, 2015
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    Counterfeit parts will use markings that are very similar to the parts their counterfeiting...

    Some counterfeits coming from China could be rejected parts that were supposed to be destroyed.

    I made the mistake of buying some microSD cards on alibaba.com with a too-good-to-be-true price. When I received them, it was obvious that they were intended to fool people who were buying SanDisk (a poor imitation of their packaging, but close enough to fool you at first glance). I thought I was buying from a SanDisk manufacturer/assembler who was trying to two time SanDisk. The parts were supposed to be XC (64GB), but had HC on the housing. I downloaded some programs to check counterfeits and found that they were all lower capacity (< 8GB) media with the controllers hacked to make them appear larger. Uninformed users would lose data once they filled the original capacity.

    I was given a full refund, but not before the person I was dealing with tried to get me to be a "good, kind, considerate, compassionate, ..." person and take a partial refund because she was a victim too and would be punished by her Boss for taking a complete loss. I told her I would take nothing less than a full refund and that I would talk to her Boss on her behalf. Naturally, it stopped there...
     
  13. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Last edited: Dec 14, 2015
  14. Rissy

    Thread Starter Member

    Nov 23, 2015
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    Yuo'll need to give me a chance before i can put up anything. I'm at work and don't have anything here. (only internet)
     
  15. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    I had only one failure with 4011's ; one died after 2 years, on replacing found that it was a 74HC03 rated at 6V, circuit with 8 4011's operates on 12V. " All inputs protected against static discharge".
     
  16. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Then we really need to see the circuit.

    ak
     
  17. ronv

    AAC Fanatic!

    Nov 12, 2008
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    Once upon a time long long ago I worked on a product that had about 4000 ICs. We built lots of these and we usually found about 4 bad IC's in each one.
    I think they are better now.
    So I'm with the other guys. It is probably your circuit. The old CMOS can have some latch up problems. You might check that out.
     
  18. crutschow

    Expert

    Mar 14, 2008
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    What is the surface of the bench that you work on made of?
     
  19. GopherT

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    Nov 23, 2012
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    It is a sheepskin with deep pile wool wrapped with latex balloons.
     
    atferrari, absf and AnalogKid like this.
  20. joeyd999

    AAC Fanatic!

    Jun 6, 2011
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    Never experienced a bad CD4000B series part in over 35 years. Never damaged one, either.
     
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