LVTTL I/O over current

Discussion in 'General Electronics Chat' started by Baron, Nov 30, 2010.

  1. Baron

    Thread Starter Active Member

    Jun 15, 2009
    I want to use the cool runner II (XC2C64A) to drive magnetic buzzer which has coil resistance of 15 Ohm . The coolruner spec defines max 20mA @ 3.3v from the I/O which is definitely not enough.In spite of that limitation, I tried to connect it the Coolrunenr and was very pleased from the sound level pressure I got.
    Does the Coolrunner contain over current protection inside(I couldn't find any mention about it)? Is there a risk of I/O burning? Or maybe the I/O will drive as much current as it can?

  2. retched

    AAC Fanatic!

    Dec 5, 2009
    ....My friend....

    Why even tempt fate? Send extra money to my address. ;)

    You should be using an transistor to switch a buss line to the buzzer.

    A current limiting (base) resistor for the transistor and a current limiting resistor to the buzzer.

    Does the buzzer have any requirements?

    As for your controller.. Its over current protection is blowing up ;)

    Actually, over heating the I/O can cause lifetime shortening, transistor problems, fuse problems, etc..

    Limit the current ALWAYS.

    The datasheet mentions nothing about current limiting. That means you design as the answer is NO. ;)