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TS3A5017: analog multiplexer for LDC1612 configuration

jo Jou
Prodigy 10 points
Part Number: TS3A5017
Other Parts Discussed in Thread: LDC1612, TMUX1208, MUX36D08, TMUX1308, MUX507, TMUX1209, SN74CBT3251, SN74CBTLV3251, TMUX1308-Q1

analog multiplexer for LDC1612 configuration

We want to use the LDC1612 from TI and connect it to 16 different coils. We found an example projects from TI [1] which does a very similar thing. We applied the schematics of this example project, but noticed that the signal gets a lot of noise from parasitic capacitances because of the matrix configuration as displayed [2]. We worked on a solution to improve the signal-to-noise ratio and came up with the following circuit [3]. This circuit connects only a single coil to the LDC1612 at a time and removes the issue of parasitic capacitances. This circuit allows us to connect 32 coils to a single LDC1612, but as you can see, it requires a lot of multiplexers.

We would like to lower the cost of the design and preferrably use at most two dual 1:8 multiplexers to connect a total of 16 coils to a single LDC1612 chip. Could you help guide us in finding the best possible analog multiplexers for our needs?

Below you will find the images and sources mentioned in this e-mail.

I hope this e-mail properly displays our needs. We would greatly appreciate your help and if you have any questions, please let us know and we will do our best to provide all required information.

Best regards,

 

[1]: http://www.ti.com/lit/ug/tidu954a/tidu954a.pdf

 

[2] image:

 

[3] image:

  • 0
    TI__Expert 5660 points

    Hello,

    Thank you for the detailed information. We do have a few 2-channel 8:1 multiplexers (such as MUX507 and MUX36D08), but they are mid-voltage devices with less features, higher Ron, and higher cost, so I don't think that is best. Could you use four 1-channel 8:1 muxes? TMUX1208 or TMUX1308 are great, newer options with modern features and lower cost.

    If you want to stick with the 2-channel 4:1 muxes, take a look at TMUX1209 which also has several newer features, including 1.8V compatible control logic, break-before-make delay, and fail-safe logic.

    What is the end equipment for this design? What key features and parameters are you looking for? Feel free to check out our product search table which allows you to sort our switches & muxes by configuration, channels, parameters, features, and cost. 

    Let me know what you think about the 8:1 muxes!

    Regards,

    Kate

  • 0 in reply to Kate Dickson
    Prodigy 30 points

    Hi Kate,

    Thank you for your response. I am working with Jo on this project and my goal is to find a suitable multiplexer.

    I think it's best to work with 1:8 switches instead of the 1:4 switches. It reduces the component count by two, decreases the trace length, reduces the amount of parasitic capacitances, and lowers the complexity of the system as a whole.

    The TMUX1208 seems like a good choice. As far as I can see, the parameters are in line with what we expected them to be. The total component count seems to end up at ~1.40usd (0.35usd per IC).

    There is one multiplexer (or actually two) which seem to beat this TMUX1208 by cost: SN74CBT3251 / SN74CBTLV3251 (only apparent difference seems to be the supported supply voltage). Do you think this component would be a good replacement of the TMUX1208 or am I missing something important?

    Thank you in advance.

    Regards,
    Eric

  • 0 in reply to Ericson64328
    TI__Expert 5660 points

    Hi Eric,

    Thanks for your interest in our 8:1 muxes. 

    TMUX1208 is a great choice because it has a wider supply voltage range, break-before-make switching, fail-safe logic, and supports 1.8V control inputs. 

    I would also like to suggest taking a look at our new 8:1 mux, TMUX1308-Q1. TMUX1308-Q1 has a lower cost than SN74CBT3251, SN74CBTLV3251, and TMUX1208, with 1.8V logic control inputs and break-before-make delay. 

    Additionally, TMUX1308-Q1 is available in a new small leaded package, SOT-23 Thin, which is a great alternative to QFN, with 0.5mm pitch!

    Regards,
    Kate

  • 0 in reply to Kate Dickson
    Prodigy 30 points

    Hi Kate,

    Thank you for the suggestions. I see that the TMUX1308-Q1 is still in preproduction. When is it expected to be available for mass production?

    Regards,
    Eric

  • 0 in reply to Kate Dickson
    Prodigy 30 points

    On another note; isn't the on-resistance of the TMUX1308-Q1 too high?

  • 0 in reply to Ericson64328
    TI__Expert 5660 points

    Hi Eric,

    That is true, the Ron may be too high for your application.

    For that reason, I think TMUX1208 is the best solution. You can expect a follow-up from me offline.

    Best regards,
    Kate