Shop OBEX P1 Docs P2 Docs Learn Events
74hc595 output current — Parallax Forums

74hc595 output current

dr_eggman198dr_eggman198 Posts: 15
edited 2005-07-17 18:13 in BASIC Stamp
I am making a circuit using a transistor for a switch, but I need to know how much current the 74hc595 shirft register can output in order to determine what type of a transistor to get.. DOes anybody know this?

Comments

  • KenMKenM Posts: 657
    edited 2005-07-17 17:54
    I don't have a number. However, if you are using the HC595 to drive a transistor that will inturn drive a load, it is very likely that the HC595 has more than enough current capacity.

    How much current will the transistor switch? If you are doing simple LED's with a common 2n3904 there will be no problem whatsoever using proper resistor values.



    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Ken
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-07-17 18:13
    When all else fails... lookup the datasheet. I found a TI datasheet for the 74HC595 that says the maximum output current is 35 mA; while the maximum device current is 70 mA. What I would do, then, is divide 70 mA by the number outputs I'm going to use.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Jon Williams
    Applications Engineer, Parallax
Sign In or Register to comment.