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 not able to design 7447A 7segment IC in Pspice 

Last post Mon, Dec 5 2011 7:21 PM by sorabhd. 2 replies.
Started by tushi 02 Dec 2011 10:37 PM. Topic has 2 replies and 1915 views
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  • Fri, Dec 2 2011 10:37 PM

    • tushi
    • Not Ranked
    • Joined on Sat, Dec 3 2011
    • Posts 1
    • Points 35
    not able to design 7447A 7segment IC in Pspice Reply

     I tried to design a circuit using 7447A IC

    the 3 connections - LT, RBI and RBO are in active low. I am not able to get valid output. What should be the inputs to these 3 connections to get a valid ouptut?

    I have not been able to get any help regarding this on the net. They all talk of 7447 with 16 pins. in 7447A, Vcc and GND pins are missing. Ignoring them also, if i attach low input to above mentioed 3 connections(since Vcc is connectd tot them in active high), then also my output is not produced as desired.

    Please help on this.

    • Post Points: 35
  • Mon, Dec 5 2011 1:54 AM

    • oldmouldy
    • Top 10 Contributor
    • Joined on Tue, Jul 15 2008
    • Woking, Surrey
    • Posts 1,410
    • Points 24,070
    Re: not able to design 7447A 7segment IC in Pspice Reply

    Check out the datasheet: http://www.ti.com/lit/ds/sdls111/sdls111.pdf

    BI / RBI must be high for "normal" operation, also the outputs are open-collector, so pull-ups will be needed at the outputs to detect any function.

    • Post Points: 5
  • Mon, Dec 5 2011 7:21 PM

    • sorabhd
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    • Joined on Mon, Dec 5 2011
    • Posts 2
    • Points 40
    Re: not able to design 7447A 7segment IC in Pspice Reply
    I simulate 7447A on PSpice. It is working fine as per datasheet. Please refer truth table in datasheet explaining the effect of LTbar,BIbar/RBObar,RBIbar pins on outputs. (Datasheet available at : http://www.ti.com/lit/ds/symlink/sn7447a.pdf)      7447A have active low outputs designed for driving common-anode LEDs. Lamp Test (LTbar) can be performed at any time when the BIbar/RBObar node is at high level.BIbar can be used to control the lamp intensity by pulsing the outputs.         So, for normal operation, put LTbar=High, BIbar/RBObar=High and RBIbar=X(don't care). Other cases are : 1).IF BIbar/RBObar=Low --> All outputs will be low.2). IF LTbar=Low and BIbar/RBObar=High --> All outputs will be High.  

    Thanks,

    Sorabh Dung

     

    • Post Points: 5
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Started by tushi at 02 Dec 2011 10:37 PM. Topic has 2 replies.