I suck at reading datasheets :(

Discussion in 'The Projects Forum' started by elimenohpee, Jan 6, 2010.

  1. elimenohpee

    Thread Starter Active Member

    Oct 26, 2008
    47
    0
    Hi,

    So I'm going through my undergraduate in EE. Needless to say, 90% of the work we do is theoretical. So when I'm going to actually build stuff in real life for my own fun, I'm having trouble finding information I need. One problem I've ran into is using a darlington array. Here's the datasheet:

    http://www.datasheetcatalog.org/datasheet2/b/0fxyuf66ess3kw8eaxa6ueweq7cy.pdf

    I don't see anywhere in the parameters what the common pin should be set at which voltage. For my application, emitter is grounded, but I'm assuming the common pin needs a specific voltage (its probably 5v) but I don't see where anywhere on the datasheet. Can someone help me out? :)
     
  2. Dalaran

    Active Member

    Dec 3, 2009
    168
    0
    Seems it can be used in a number of different ways. What is your application?

    Check out page 11, "Application Information" for some typical layouts.

    edit: and BTW, common to me usually means "Ground" and not 5V.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    If your load is inductive, connect the COM pin to the Vcc of the output load.
     
  4. elimenohpee

    Thread Starter Active Member

    Oct 26, 2008
    47
    0
    I thought the same thing, but the darlington array is an array of transistors. The base is obviously the input, the emitter is well known as it's labeled E on the pinouts. That only leaves COM to be the collector. There has to be a voltage at the collector to actually amplify the current. I don't know, maybe I'm thinking about this completely wrong. I'm only trying to power an array of leds haha :(
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Well, you don't really need to use the COM terminal then.

    The outputs are open collector.
    1B through 7B (pins 1-7) are the base inputs.
    1C through 7C (pins 10-16) are the open-collector outputs.
    E (pin 8) is the emitter; goes to GND.
    COM (pin 9) can go to the Vcc of the LEDs, or you can use it to provide a TEST function by using a N.O. pushbutton switch to connect it to GND.

    Note that the open collector outputs can only sink current; they cannot source current.
     
  6. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    Over the years I've used these chips many times, ordered 1K once. I've always been curious why they labeled that pin Com as I've always connected it to the Vcc. At the expense of exposing an embarrassing duh moment, it makes sense now! ;)
     
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