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TMUX1574: THD for 20Hz to 20kHz with 32Ω Resistor

Hao Wang14
Expert 4415 points
Part Number: TMUX1574
Other Parts Discussed in Thread: TS5A23157

Hi Team,

TMUX1574 is considered to be used for audio switch, what's the THD of 20Hz to 20kHz if the RL is 32Ω?

Usually the THD in datasheet has test condition that RL is 600Ω, when RL decreases, will THD be better or worse?

Thanks and best Regards!

Hao

  • 0
    TI__Mastermind 46347 points

    Hi Hao,

    I am checking if we have data for THD + N for the 1574 - but I am not sure if we have it. That being said I can give you a little insight of the factors that improve degrade THD+N.

    For an Analog mux the biggest contributing factor to distortion is the On Resistance of the Multiplexer Versus input Voltage (On Resistance - Ron) because this is a non-linear effect, i.e. the voltage divider between load and mux is non-linear and can cause distortion due to this effect. The larger the Ron flatness value is, the worse the THD+N performance will be. However this is highly dependent on load - the smaller the load is relative to the on resistance flatness of the multiplexer the more distortion will occur.  So decreasing a 600 Ohm load to a 32 Ohm load will degrade THD+N performance by quite a bit. The TMUX1574 has a worse case flatness of 1.8 Ohms which is almost 1/16 of the total load size - this part may have a higher THD+N than needed for the application as the worst Ron performance is at the higher input voltages - this means that more degradation will happen at the fundamental frequency compared to the to the harmonics which would also increase THD+N.

    Can I ask why you are looking at the 1574 for Audio?  This part is typically not recommended for Audio - and we do have parts such as the TS5A23157  which have a lower worst and typical case THD+N Performance than the 1574 and has a typical THD+N at 0.01% at a 4.5V supply.

    Please let me know if possible why the 1574 is being looked at and not one of our audio switches - because I don't think the 1574 is our best offering for the application.

    Please let me know!

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    TI__Expert 4415 points

    Hi Parker,

    Thanks for the detailed explanation, we will consider TS3A23157 for the audio application. I remember there is an app note about THD and Ron flatness relationship, but I cannot find it. Could you please share the link if you happen to know? Thanks!

    Best Regards!

    Hao