• State TI Thinks Resolved
  • Locked Locked
  • Replies 9 replies
  • Answers 2 answers
  • Subscribers 18 subscribers
  • Views 394 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

CD74HCT4067: Increase output current

May
Genius 9880 points
Part Number: CD74HCT4067
Other Parts Discussed in Thread: TMUX1208, TMUX1308, SN74CBT3251

Hi,

Just to confirm, to increase the output current of the I/O can the cd74hct4067 be cascaded like parallel memory one on-top of the other?

 

Thank you in advance.

Regards,
Maynard

  • 0
    Guru 281490 points

    That would be possbile. A closed switch behaves much like a resistor, so you then have multiple resistors in parallel.

    But it might be a better idea to use two 1:8 muxes with better Ron (e.g. TMUX1208), and to add logic for the correct channel selection (connect A3 to EN, for one of them with an inverter).

    How much current do you need, and what is the voltage drop you can afford?

  • 0
    TI__Genius 10974 points

    Hi Maynard,

    While paralleling these devices would allow for an increased output current as the current would be split between the two switches, the problem you need to account for is switching these at the same time which is not guaranteed. The two multiplexers will almost certainly have different switching characteristics and if one switch turns on before the other, this means all that current will be flowing through one switch and if it is higher than the maximum rated channel current, it could damage the device. This practice is only advisable if you will be switching with no load present on the switch to ensure everything has settled and both channels have been completely enabled.

    Thanks!

    Bryan

  • 0
    Prodigy 40 points

    My sigle channel output current would be 90ma when all three LEDS of the RGB are ON. I require a Tmux 16:1 single- ended channels,

  • 0 in reply to Xavier Davila
    Prodigy 40 points

    I'm also not sure in using the ULN2803A device is a 50 V, 500 mA Darlington transistor array with outputs that are always on because my project is for clothing and the 16 outputs can't be on all the time a short circuit or wires touching the human is not good at 16 x 500ma. which is why i need a tmux 16:1 having only one I/O active at a time. Each I/O to sink only 75 to 90ma.

  • 0 in reply to Xavier Davila
    TI__Genius 10974 points

    Hi Xavier,

    Can you help provide a schematic of your proposed application? Most likely the CD74HCT4067 will not work due to the current requirements being too large (this device can only handle 25mA per channel). You will probably need 2 8:1 multiplexers with higher current capabilities such as the TMUX1308 or SN74CBT3251.

    Let me know if you can help clarify the exact way you are proposing implementing your application and I can help further suggest a solution.

    Thanks,

    Bryan

  • 0 in reply to Bryan Marshall
    Prodigy 40 points

    Yes finally the SN74CBT3251 will work. Now is there a 1-of-16 FET Multiplexer and Demultiplexer that would be perfect if such device can be found and if not why hasn't it been produced. There are many high current 1-of-16 Multiplexer and Demultiplexer with serial data input all of which I can't use due to the serial data constraint not used. MAYBE THERE A MIRACLE IC FOR ME.

  • 0 in reply to Xavier Davila
    Guru 281490 points

    There are not many 1:16 muxes because you can easily construct one from two 1:8 muxes and a NOT gate (connect the fourth address signal to both enable pins, for one of them inverted).

  • 0 in reply to Xavier Davila
    TI__Genius 10974 points

    Hi Xavier,

    We do not have such a high current capable 16:1 mux. 2 8:1x1 channel muxes would be your best bet for the application you are trying to achieve. So 2x TMUX1308 or SN74CBT3251 would be what you want for this.

    If there is anything else I can do to help with this inquiry, let me know.

    Thanks!

    Bryan

  • 0 in reply to Bryan Marshall
    Prodigy 40 points

    OK thanks case resolved