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SN7406: I need a different logic family.

bkmtech
Prodigy 230 points
Part Number: SN7406
Other Parts Discussed in Thread: CD4049UB, TPL7407LA

Greetings everybody.

Thanks in advance for you reply.

I have been using a SN7406 successfully to control an LED.

But I have been using this in a 5V system and now have a need to perform the same function in a 12V system,.

The SN7406 can handle up to 40ma of current.

In my 12V system I need curent capability only up to 20ma minimum.

There seems to be so many logic families I am not sure which to consider.

The inputs will be driven by a CD4011, although there may be a different logic family that may be better suited for that function also.

  • 0
    Prodigy 230 points

    Hi

    I can only assume I don't know how to look for parts because it should not be this hard!

  • 0
    Guru 242650 points

    The only logic family going above 5 V is CD4000. But even the CD4049UB is not rated for more than 18 mA.

    Consider a non-logic device like the TPL7407LA.

  • 0 in reply to Clemens Ladisch
    Prodigy 230 points

    Thank you for your reply and nedless to say I am not happy with it!

  • 0 in reply to bkmtech
    TI__Guru* 96591 points

    Hi bkmtech,

    If you can power the logic from 5V, then the output will support up to 30V and 40mA:

    Have you considered just using a MOSFET or BJT? Making an inverter with either of those is just the component + a resistor or two. These are typically the easiest way to drive power from a low voltage input signal to high voltage component. The TPL7407 that Clemens recommended is a good solution, but may be overkill for your application since it has multiple channels.

  • 0 in reply to Emrys Maier
    Prodigy 230 points

    Yes, I could power it from 5v if I also wanted to run 5v power to my board, but this is not practical.

    Yes, I could and probably will use discrete parts.

    I just don't understand why this is even a problem in the first place.

    The SN7406 was such an uncomonly used part that no equivalent part was made to work at a higher voltage.

    I appreciate all your replies but I am not pleased with what is available, plus the TPL7407 is not a through hole device.

    My issue was not resoleved successfully.

    It happens.

    Thank you for trying!

  • 0 in reply to bkmtech
    TI__Guru* 96591 points

    I can tell you why -- logic voltages don't increase with newer technology, they decrease. 

    The oldest logic started at 5V, but processor designers found that by reducing the voltage to 3.3V they could reduce the size and power consumption of devices by a factor of 0.7 and thus get double the transistors per chip (hence Moore's Law). This trend continued for many years and today most high-end processors operate at 0.7V or less.  The vast majority of systems operate at 1.8V or 3.3V, with some still using 5V, and we almost never see 12V or higher logic.

    The simple fact is that technology follows demand - there's very little demand for 12V logic, so there isn't much of it.

    I find it frustrating, too when I want to build something at home -- I much prefer to work with through hole components and 9V or sometimes 12V systems.  Unfortunately, those are becoming less and less available these days.

    As for the resolution - on this forum, "resolved" means we've done what we can to help you. So, when someone else comes with the same question, we'd prefer they read this thread rather than have to make a whole new one and get the same explanation again -- with the "Resolved" tag, they would know that we can't do anything else to help and they are more likely to read the thread.

  • 0 in reply to Emrys Maier
    Prodigy 230 points

    Hi

    I consulted with my client and have decided to follow some earlier advice and run 5V as an alternate source to my secondary board so I can use the SN7406, as the output is voltage independent as long as I don't exceed the current rating.   I am re-designing my main board so I need to make interface improvements there.

    I am an experienced technician so working with SMD components is not typically problematic but many of the clients I design PCB's for are not that adept with SMD, so I got caught in a bind.

    Thanks

  • 0 in reply to bkmtech
    TI__Guru* 96591 points

    Please come back any time!