LM3914 Vcc Vs Vsig?

Discussion in 'General Electronics Chat' started by tracecom, Jan 17, 2016.

  1. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    I have found that the LM3914 works with a signal voltage that peaks at Vcc, which in my circuit is 3.3V. Am I misreading the datasheet or is this to be expected?

    Thanks.
     
  2. Lestraveled

    Well-Known Member

    May 19, 2014
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    It depends on how you have the reference set up. How about a schematic??
     
  3. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    That is correct in general. If your input signal is greater than Vcc, you can attenuate it with a voltage divider (pair if resistors in series).


    If your signal is smaller than Vcc, and you want to use the full scale, there is a reference pin that lets you select the max range t something less than Vcc.
     
  4. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    I haven't drawn a schematic yet, but have been working against the application drawing on page 2 of the TI datasheet. Essentially, I am using a pot connected to Vcc and ground with the wiper connected to the sig input of the LM3914 to light 10 leds proportionately to the pot setting. It seems to work, but I am surprised.
     
  5. crutschow

    Expert

    Mar 14, 2008
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    About what?
     
  6. Lestraveled

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    May 19, 2014
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    OK, per fig. 1 on page 2 of data sheet.
    The reference is scaled for a voltage of 5 volts. Since the Vcc is only 3.3 volts, the results you are getting are reasonable.
     
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