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MUX509: How about the transition time when higher 90% of the transition?

Lucas Ding
Prodigy 320 points
Part Number: MUX509
Other Parts Discussed in Thread: ADS8686S

Hi team,

My customer has a strict requirement on the transition time when switch one channel to another channel, and we always define the time of 90% rise/down transition, but how about higher 90%, is there any lab test data to show the time at 99% even higher?

The application is switch each channel through MUX509 then send to SAR ADC ADS8686S, and the customer find the error will be 4.8% between ADC result and the scope after 15us, and 0.28% after 25us. so they want to know the data to make a balance between the accuracy and speed.

Thanks. 

  • 0
    TI__Mastermind 43536 points

    Hi Lucas,

    We don't have this data. However one note that I should mention is that the transition time is also going to be affected by the loading conditions - which the SAR ADC used does not have the same load impedance that we have tested in our loading conditions. 

    That being said - I am not 100% sure the mux is the slowest part of the system - it seems that the SAR ADC being used has a decent amount of front end circuitry which gives it an eq. circuit of a RC circuit. At a minimum it seems R is 850k and C is typically 10pF  which will take a bit of time to reach less error - and seems more in line with the results that your customer is seeing. I think if the mux was by-passed there would still be a decent delay. I'd suggest that testing a range of times would be the best approach since the results are going to be more specific to this exact application and won't be as generalized as we have in the datasheet.

    If you have any other questions please let me know!

    Best,

    Parker Dodson