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SN74LS122NSR Unused input pins

Hari T O
Prodigy 100 points

Hi Friends,

I am using a retriggerable monostable multivibrarator for one of my application. Could you please tell me how to terminate the unused pins of that chip.

Regards

Hari

  • 0
    TI__Mastermind 46480 points

    all outputs can float. All inputs should be tied high or low. If the gate is not used you can ground Rext/Cext

  • 0 in reply to Chris Cockrill
    Prodigy 100 points

    Hi Chris,

     Thank you very much.What about the Rint pin.I am sending the schematic along with this mail.This monoshot is

     part of my pulse frequency modulator.Please check it and let me know.I am sending the TINA TI simulation file and complete schematic along with this mail.Please go through it.Expecting your valuable suggestions

    Thanks&regards

    Hari T O1616.MOD DEMOD.pdf8535.codec1.TSC

  • 0 in reply to Hari T O
    TI__Mastermind 46480 points

    Hi Hari. I was looking at the LS123 when I replied before. I thoulght you were asking what to do withe the unused gate.

    You will need to connect either Rint or Rext to get you desired pulse width.  If you use Rext  then you will float Rint pin.

    Look at the application information at the end of the datasheet for instructions on how to pic the R/C values to get the desired pulse width. There is a formula and also charts with R/C vs pulse width.

    If you look at the charts you will not be able to get a 20ns pulse from this part.  We dont have a part that can generate a pulse that small. 

     

  • 0 in reply to Chris Cockrill
    Prodigy 100 points

    Hi Chris,

    Thank you very much for your time and concern. If you don't mind could you please suggest some other methods for Pulse frequency  modulation.I need to do pulse frequency modulation upon a signal coming from UART.My requirement is given below

    Frequency for ‘1’ 62.5Mhz : Frequency for ‘0’ 15.625Mhz: Duty cycle 50%: Power supply 5V

    Regards

    Hari

  • 0 in reply to Hari T O
    TI__Mastermind 46480 points

    I am not familiar with this type of application but you might look at this part. TL5001A

    There is probably a better forum to support your request but I am not sure which one it would be.

    YOu might try searching the forums for a similar application as yours