Should I use pull up?

Discussion in 'The Projects Forum' started by skybox, Jun 7, 2010.

  1. skybox

    Thread Starter Active Member

    Mar 2, 2009
    68
    1
    Hi guys,

    I was wondering if I shoud use a pull up resistor in this case?

    Pin 1 is a enable pin for the mux input A (active low). I would send a logic low from the microprocessor to enable it.

    [​IMG]
     
  2. Bychon

    Member

    Mar 12, 2010
    469
    41
    What's the part number and where is the specsheet?
     
    skybox likes this.
  3. skybox

    Thread Starter Active Member

    Mar 2, 2009
    68
    1
  4. Bychon

    Member

    Mar 12, 2010
    469
    41
    There isn't a word about Enable on that specsheet, except 1 is disable and 1 is at least 2 volts. I would guess the next step is to search Pericom for the "family" characteristics...unless somebody else here knows the answer.
     
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  5. skybox

    Thread Starter Active Member

    Mar 2, 2009
    68
    1
    I believe when ENa is low, all of the A switches (s1a, s2a, s3a, s4a) are enabled. Vice versa for ENb.

    From there, depending on the value of IN1 and IN0, you can have specific switches go off and on.
     
  6. Bychon

    Member

    Mar 12, 2010
    469
    41
    This app note in the PI5 family shows a 4.7k pull up resistor.
     
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  7. Hardware Freak

    New Member

    Jun 11, 2010
    7
    1
    Hi Guys..!!

    Pins with TTL logic family shud always be pulled- high or low through a resistor...
    The value of the resistor depends on wat voltge ur r connecting the resistor to and also on the sink curent capacity of the IC...
    If TTL pins are left open/float they act as antennas.

    Hence u should connect a pull-up resistor to the pin
     
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