CD4528 max pulse width

Discussion in 'General Electronics Chat' started by kgstewar, Sep 28, 2012.

  1. kgstewar

    Thread Starter Active Member

    Apr 5, 2012
    152
    6
    Hi all,

    I need a one-shot monostable vibrator that delivers a positive pulse that is about 5 seconds long (+/- about a second). I have a bunch of CD4528s and they seem to fit the bill but in the data sheet I could not find a value for the maximum pulse width that it can deliver. I can certainly calculate a resistor/capacitor combo that gives me the required pulse width but I was wondering if there is a maximum value for this component that I may be exceeding.

    Thanks!

    Kevin

    P.S. Data sheet attached
     
    Last edited: Sep 28, 2012
  2. MrChips

    Moderator

    Oct 2, 2009
    14,881
    4,441
    There is no maximum. Make C as large as you wish.
     
  3. kgstewar

    Thread Starter Active Member

    Apr 5, 2012
    152
    6
    Thanks Mr. Chips!
     
  4. İsmail Sahillioğlu

    New Member

    Feb 26, 2017
    3
    0
    Hello!
    Although this message is 4 year-old, I'd like to share this information fot those who seek for exact information about these ICs.
    The 4528 IC is not an exact timing delay chip. According to OnSemi's datasheet; this IC only has a pulse width from 550 nanoseconds to 100 microseconds. Maximum timing delay configuration with this chip and external RC network must not exceed the 100us pulse width on its output.
    So if you want to generate large timing delays use 4541 (max pulse width = 5 mins) or 4536 (max = 23 hours) in this serie. Or you can also use 4047 Monostable/Astable Multivibrator.

    Here is the OnSemi's datasheet link: http://www.onsemi.com/pub_link/Collateral/MC14528B-D.PDF
     
  5. DickCappels

    Moderator

    Aug 21, 2008
    4,234
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    Do you realize that those two are not in the same family?
     
  6. hp1729

    Well-Known Member

    Nov 23, 2015
    2,309
    282
    For long time constants using high loss capacitors you might find it useful to use a diode or transistor as shown in the examples shown in the attachment. I don't think it would work for retriggerable applications though.
     
  7. İsmail Sahillioğlu

    New Member

    Feb 26, 2017
    3
    0
    I didn't understand Mr Cappels, what family do you talk about?
     
  8. DickCappels

    Moderator

    Aug 21, 2008
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    Upon a third look I see they are both B series CMOS. For some reason when I posted the comment I thought the Fairchild part was A series.

    Still, the specifications for the two are different, and the reason ON Semiconductor suggest not going beyond 1 second is because ON has parts that do a better job of timing long periods. And it may be that Fairchild supports their part for longer delays because they don't have anything better to offer. Its marketing, not engineering.
     
  9. İsmail Sahillioğlu

    New Member

    Feb 26, 2017
    3
    0
    I see, yes you're right about that Mr Cappels. However I tried out NXP's chip and configured as a nonretriggerable multivibrator. I connected an RC network 100k and 100uf, and then yeah it shooted a pulse width out approximately 2 or 3 secs and I think it was its max. Even so, it's normally limited out from factory with 1milisecond limitation, it's shown in its parameters in page 7. Here is the link for its datasheet from NXP.

    http://www.nexperia.com/products/logic/specialty-logic/multivibrators/series/HEF4528B.html
     
  10. DickCappels

    Moderator

    Aug 21, 2008
    4,234
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    This thread is about the Fairchild part. Figure 1 of the datasheet shows the RC values for various pulse widths going out to 5 seconds. Since the question is about the Fairchild part, arguments that a different part is not recommended by a different manufacturer has little merit other than to show that when substituting parts, one cannot simply go by the part number.
     
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