ADG408/409 LTSpice Transient Analysis

I've been trying to perform a basic transient analysis within LTSpice using the ADG408 multiplexer, and have been getting very strange results:

  • The output voltage spikes when the address is changed, but the corresponding switch input is not transferred.
  • A substantial amount of current is sometimes drawn at the switch inputs.
  • Changing the enable input seems to have no effect.

I've tried a variety of configurations, and have been unable to get the model to work as expected. Is this a limitation of the model or LTSpice, or am I doing something incorrectly?

I've attached the LTSpice schematic and symbol I created, along with a screenshot showing the unexpected behavior. The A2:A0 pins are driven with 3.3V pulse sources configured to produce a 3-bit binary count pattern.

The ADG409 Spice model produces similar results.

attachments.zip
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  • Hi Caleb,

    I tried to check on your circuit and it looks like the symbol file does not call the spice model properly.

    You might want to update your symbol file and here's what you can do:

    1. Open the ADG408.asy
    2. Update the netlist order of the pins. S1 should be numbered 1 instead of 4. S2 should be 2 and so on.

       3. Click on the save button and try to simulate again.

    Kindly take note that LT spice symbol follows the numbering convention 1 to n instead of the node names. 

    Also, for easier generation of LT spice symbols, you might want to check on the reference article below.

    LTspice: Simple Steps to Import Third-Party Models | Analog Devices 

    Let me know if this helps.

    Best Regards,

    May

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