Sink & Source Driver ICs - Current Limits & Replacements

Discussion in 'General Electronics Chat' started by elec_mech, Jun 18, 2012.

  1. elec_mech

    Thread Starter Senior Member

    Nov 12, 2008

    I'm using a ULN2004 and UDN2981/2 IC in a couple of LED circuits to sink and source, respectively. The ratings on both of these ICs is 50V, 500mA per output pin. Is it safe/smart to use these ICs in applications requiring close to 500mA, say 450mA?

    Per SgtWookie, I know while a standard transistor like a 2N3906 is rated up to 200mA, it's best not to put more than half of that (100mA) through it. Should this same derating safety factor (~50%) be used for driver ICs as well, specifically the ULN and UDN families?

    If not, can anyone recommend other ICs that can sink/source 450mA safely? I know I can use individual transistors or MOSFETs with higher ratings, but I'm trying to conserve board space.

    On another note, the UDN2981/2 has been my favorite source IC for some time, unfortunately these appear to be discontinued. I found this as a replacement: Any reason these won't work the same as the UDN2981/2? Just looking for another readily available source IC.

    Any advice is appreciated. Thank you in advance.
  2. takao21203

    Distinguished Member

    Apr 28, 2012
    If you have doubts about this, I suggest to cool these ULN ICs, maybe using a cooling grid for 4 ICs together.

    Do you talk about SMD digital MOSFETs? I know one that can handle 2 Amps:

    The TMS2302, and Radionics has these for good price.

    8x of these = not much larger than a DIL IC.

    LEDs are not critical = static loads, small bulbs or motors are different, inrush current = higher.

    Important = to keep IC temperature less than 80C.

    For myself I consider any component that is uncanny to touch = too hot, needs cooling, or change to different component.