SN75173 >45mA?

Discussion in 'The Projects Forum' started by owhite, Jan 29, 2014.

  1. owhite

    Thread Starter New Member

    Jun 11, 2010
    4
    0
    Folks I'm using a differential line receiver (SN75173) and it's drawing 45mA which seems like it's a lot higher than suggested from the specs.

    The circuit is here.

    At present the connections to the bus that serve as inputs are not connected to anything. The outputs (pins 3, 5, 11, and 13) are connected to an I/O board plugged into the PCI slot of a computer.

    Any suggestions for why the draw is so high? I have a few of these in my circuit and I just surprised by the overall current. I'm using proteus software which supports circuit modeling and it's reporting that the draw should be much lower.

    thanks,
    owen

    [​IMG]
     
  2. crutschow

    Expert

    Mar 14, 2008
    12,991
    3,227
    What are the loads on the outputs? Could they be low impedance, such as 75 ohms?
     
  3. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,516
    1,246
    From the TI datasheet, the max static current is 70 mA with the outputs disabled. I've used similar parts; they are hungry and they do run warm.

    ak
     
    #12 likes this.
  4. owhite

    Thread Starter New Member

    Jun 11, 2010
    4
    0
    Thanks - I was just mis-reading the spec sheet - looks like 45mA is not too unreasonable.
     
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