Circuits Stuff

Discussion in 'General Electronics Chat' started by frustratednoob, Jan 19, 2013.

  1. frustratednoob

    Thread Starter New Member

    Dec 21, 2012
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    Hey guys, I have trouble figuring out the purpose of some components.

    1. HIH-5031 Humidity Sensor
    http://www.farnell.com/datasheets/1676925.pdf
    Under the typical application circuit, was wondering what is the minimum load between the -ve and +ve terminals for?

    2. TPS61221DCK
    http://www.ti.com/lit/ds/symlink/tps61222.pdf
    Under the typical application circuit for the fixed output voltage option, was wondering what C1, C2, and L1 are for?

    PLEASE HELP! :(
     
    Last edited: Jan 19, 2013
  2. MrChips

    Moderator

    Oct 2, 2009
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    Are you going to be frustrated for the rest of your life or are you going to become happymember one day?
     
  3. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    You need better glasses, the minimum load is between OUT and -Ve, and it has to be 65kΩ or less.
    C1 is input capacitor, L1 is the main inductor that stores energy for boosting the voltage and C2 is the output capacitor where this energy gets dumped.
     
  4. MrChips

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    Oct 2, 2009
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    I know this is ambiguous when they say minimum load is 65kΩ.
    But I think they are correct and mean 65kΩ or greater than 65kΩ.
     
  5. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Now that I think about it it makes more sense to be minimum load resistance a.k.a. maximum load. Wonder why even such rescpectable company as Honeywell can't make correct and inambiguous datasheets.
     
  6. frustratednoob

    Thread Starter New Member

    Dec 21, 2012
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    Thanks for you explaination, but is there any particular reason why is the voltage for C1 and C2 specified to be 6.3V at 10µF? I understand that X5R stands for the capacitive tolerance and max/min operating temp.

    And for the minimum load question, sorry for that mistake on my part..
    But by I'm having a hard time udnerstanding "minimum load". Shoudln't it be like "Maximum load" or something? And in that way, isn't the resistor just meant to resist the voltage passing to the -ve terminal?

    (Sorry for my bad english, English isn't my first language. :( )
     
  7. Audioguru

    New Member

    Dec 20, 2007
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    Because they hire little kids straight out of skoooool to write the datasheets.
     
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  8. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    The voltage ratings are just what they used in the test circuit from which the typical curves are obtained, you need to select proper voltage rating according to your input and output voltages.

    Look at pages 13-15 where they show the design process, C1 minimum recommended value is 10uF, C2 should be at least 4.7uf, but 10uF is reccommended.
     
  9. WBahn

    Moderator

    Mar 31, 2012
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    I haven't looked at the data sheet, but it could be either way. A number of circuits have to have a minimum load, as in minimum current draw, in order to work properly. Perhaps that is the case here. Others, of course, have a maximum load and you shouldn't draw more than a certain current from them. There are probably enough clues in the data sheet to figure out which is meant, but it definitely should be clearer.
     
  10. crutschow

    Expert

    Mar 14, 2008
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    I interpret it as meaning 65KΩ minimum load (resistance). Otherwise they would need to state a maximum load, but I think the maximum load is open circuit or infinite resistance.
     
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