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SN74LVC1G86: IC performance without Bypass capacitor.

Kunal barot
Intellectual 605 points
Part Number: SN74LVC1G86

HI Support

WE have used SN74LVC1G86  , Xor Gate . where two  digital IO from micro-controller goes to this X-OR inputs. Both have 2.2K pull up resistor. we have one 0.1uf ceramic cap on Power supply line of this X-or IC.

so ideally when both the IO are same , Xor Output will be Low and  when both IO are different then Xor Output will be high.

we have observe one unit which was kept at 50C ambient forma month , that byapss capacitor on IC pin have one end dry solder. (see below comment)

***************************************************

We bring out the unit form test chamber.  and observe

C34 , (0.1uf/50V) one end was dry , although have connectivity , but once try to touch solder at one end of capacitor it came out.

Section:- Relay X-OR IC Bypass capacitor.  

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I want to know what can happen if bypass capacitor was got disconnect , what are the possibility. can x-or IC behave opposite (like X- Nor). 

  • 0
    TI__Guru* 96591 points
    Hi Kunal,
    No, the internal logic will not change because of the removal of an external supply filter capacitor, however the output will likely have more noise. In most cases, this will not cause any issues.

    The bypass capacitor has two primary purposes:
    (1) Provide a local charge well to power the IC. This allows for quick delivery of charge to the device (ie current) when it is required for operation -- in logic, this is when the inputs are switching. Without the bypass capacitor, all charge has to be sourced from the supply, wherever that is. It's possible to see the supply voltage drop significantly at the device during these transitions without the capacitor, and that can lead to poor quality output (noise) or even erroneous outputs in extreme cases.

    (2) Filtering out power supply noise. The capacitor provides a short to ground for high frequency content on the power supply line, providing a smoother output for the device.

    If this resolves your question, please click the green "this resolved my issue" button -- if not, please respond and I will continue to help.