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TMUX7234: for Microphone audio signal

Henry Wang3
Genius 3215 points
Part Number: TMUX7234
Other Parts Discussed in Thread: TMUX2889

Hi Sir,

My customer is going to use TMUX7234 to act as an analog switch to pass Microphone audio signal (as we know, mic signal is always very weak and maybe down to several milli-volt).

Because they are not able to get an EVM to make a quick measurement in time, could someone there advise me if its THD+N and SNR will be deterioated with such design ?

  • 0
    Prodigy 80 points

    Thanks Henry !

    It is worth mentioning that Ihe VDD and VSS to TMUX7234  is +5V and -5V.

    SG

  • 0 in reply to See Guan Huan
    TI__Mastermind 32883 points

    Hey Henry, SG,

    Can you expand on what you mean by deterioted? Relative to what exactly? Adding any passive like an analog mux to the system will have some affect on the THD + N so I would expect the SNR to decrease a bit there but if you mean using the mux with those supplies vs another supply level then that's a different question. Using the TMUX7234, a 44V mux, at +/-5V would actually yield in a little worse performance, relative to say +/-15V, since you're at the very low end of it's operation capabilities. That being said, we do have the +/-5V condition in the datasheet already for THD + N. 


    That being said, if the 0.002% THD+N is a little too high for you, you can consider the TMUX2889 which would let you use a single supply but pass +/-5V and is really designed to handle lower frequency audio signals. Do you know what frequency the signals are?

    Thanks,
    Rami 

  • 0 in reply to Rami Mooti1
    Prodigy 80 points

    Hello Rami,

    Thanks for your prompt response. I just want to get an idae, if any negative impact to THD+N and SNR will be if a very low level audio signal (20Hz ~20KHz) passes though the switch. I agree that adding any passive analog mux would yield a bit noise to the performance, I just wonder how much the noise level may have. So I am seeking for suggestions/comments from TI people who has experienced with this device.

    TMUX2889 does look a better choice but I do not like its footprint as it may be a problem to me when soldering it. 

    Anyway, I think TMUX7234 is acceptable in my current applications now, I will apply it to the circuit design of the amplifier.

    Best wishes,

    SG

  • 0 in reply to See Guan Huan
    Prodigy 80 points

    Hi Rami,

    Can you advise the THD+N in frequency >7KHz ?

    Thanks.

    SG

  • 0 in reply to See Guan Huan
    TI__Mastermind 32883 points

    Hey SG, 

    I was able to pull a wider range that encompasses the typical audio 20kHz that you're looking for. Looks like it actually improves a bit

    Thanks,
    Rami

  • 0 in reply to Rami Mooti1
    Prodigy 80 points

    Thanks Rami. Why it improves a bit across high freq. range ? Is it caused by external LPF ?

    SG

  • 0 in reply to See Guan Huan
    TI__Mastermind 32883 points

    Hey SG,

    I believe you're correct here. There is some filtering here in the setup they typically use to remove some of the higher frequency harmonics to keep the integrity of the signal in the audio range. The dip does start a bit earlier than expected though. For safe measures, I'd really design with the the flat region in mind (~ 0.0020%) if I was in your position

    Thanks,
    Rami 

  • 0 in reply to Rami Mooti1
    Prodigy 80 points

    Thanks for the feedback Rami.