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MUX36D04: Programmable output current

Roy Chou1
Genius 16130 points
Part Number: MUX36D04

Hi Team,

Can below confit workable?

Regards,

Roy

  • 0
    Guru 317060 points

    Yes. But the MUX36D04 has a typical Ron of 125 Ω, which would result in a large voltage drop for large currents. I do not know if this matters in your application.

    Instead of having four complete circuits, you could simply switch four different R1s.

  • 0
    TI__Mastermind 35608 points

    Hey Roy,

    Just double up on Clemens answer here, yes it will work but like he mentioned 125ohms may be too large (or it may not matter). That being said, is there a reason 4 of the exact same circuit are being muxed? Or is something (R1) changing in these four circuits?
    If the R1 is changing then I'll back what clemens is suggesting. You could simply use only one of those circuits and only mux the R1 value between the 4. That way you'll reduce the FET count and Diode count of your overall circuit. Plus is R2 is remaining the same, you'll only need 1 vs 4 you'll need in this current implementation. 

    Thanks,
    Rami

  • 0 in reply to Rami Mooti1
    TI__Genius 16130 points

    Hi Rami,

    Ron(125ohm) is ok for us. Is below connection ok?

    In addition, if we want to use R1 to let Iout < 1uA, we can't guarantee the accuracy, is it correct?

    Regards,

    Roy

  • 0 in reply to Roy Chou1
    TI__Mastermind 35608 points

    Hey Roy,
    Your image is close but I can't tell what you're doing with the diode. Here is what the circuit would look like: 

    Roy Chou1 said:
    In addition, if we want to use R1 to let Iout < 1uA, we can't guarantee the accuracy, is it correct?

    I'm not sure I follow what is being asked here. If we want <1uA, it looks like 1.24/R1 needs to be less than 1uA. So as long as R1 is substantially large then it will be fine. The mux will add 125ohms but it seems here that the resistance will need to be in the Mega-ohm range to get <1uA so the mux shouldn't really impact much.

    Thanks,
    Rami