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low output impedance MUX

Discussion in 'Electronic Design' started by mook johnson, Apr 10, 2004.

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  1. mook johnson

    mook johnson Guest

    I have a requirement to drive 32, 5 volt devices, with a 10mA current draw
    each. I'd like to power each one on, one at a time, and cycle through
    several times per second.

    Does anyone know of a 1:8 or 1:16 mux (or device with similar functionality)
    that has an output impedance lower than 10 ohms?
     
  2. Rich Grise

    Rich Grise Guest

    http://www.fairchildsemi.com/ds/74/74AC138.pdf

    It's usually not expressed as an impedance, but the spec sheet calls out:

    Vol: Maximum LOW Level Output VOltage, at Vcc= 4.5V, max .44V at Iol = 24
    mA.

    That's for a low side driver - high side is only guaranteed to give you
    3.76V
    at -24 mA.

    There are lots of others, that's just the first one I looked at. You'd need
    4 chips, and of course, the counter.

    Have Fun!
    Rich
     
  3. GPG

    GPG Guest

    Since '138 is active low inversion is required to switch high side.
    Could buffer with http://www.fairchildsemi.com/ds/2N/2N3906.pdf
    50 mV VCEsat
     
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