Does the LTspice model of ADG1434 also model the CS/CD (ON/OFF) capacitance?

In addition to that, what are the other parameters that are modeled in LTSpice model?

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  • +1
    •  Analog Employees 
    on Feb 12, 2021 4:51 PM

    Hi, paulplusx.

    Our switches and multiplexers have the following parameters included in the LTspice model:

    • On-Resistance (The twin-peak curve at +/-15V for the ADG1434, but operational in the entire voltage range of the device)
    • Charge Injection
    • Timing (Ton, Toff, Tbbm, Ten)
    • Bandwidth
    • Off Isolation
    • Crosstalk (Models other than SPST devices)
    • Fault Protection (For models from the Fault Protected Switches portfolio)

    However, these specs are NOT included in our models:

    • Leakage Currents
    • Capacitance (with the exception of the logic input)
    • SPI

    Do you require the ADG1434 capacitance to be exactly like in the datasheet?

    What other parameters are you interested in?

    Could you describe a bit of your application, maybe we can come up with a solution without having to modify the LTspice model?

    Yours sincerely,

    Igor Ono.

  • Hi Igor,

    Thank you for the information. My main issue is driving multiple analog switches (capacitive load) with AD817, I have described everything here: https://electronics.stackexchange.com/questions/548062/how-to-properly-drive-parallel-analog-switches-variable-capacitive-loads-with/

    If you see the link I also have a requirement of low on-resistance (along with low on capacitance) hence I came to a compromise with AD1434. If you could suggest something else, please feel free to do so.

    Regarding your answer that the switch models don't model Capacitances, I am a bit confused since when I look at the ADG613.cir file, I see the below (Cs/Cd off - mentioned):



    The file formally says the same things that you mentioned but then what is the above code for? Is it not modeling the Cs/Cd capacitance?

    Best regards,
    Shubham

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  • 0
    •  Analog Employees 
    on Feb 18, 2021 12:38 PM in reply to paulplusx

    Hi, Shubham.

    Regarding device recommendations, the ADG1434 would be a great choice for a compromise between on-resistance and capacitance, as well as packing 4 SPDT switches inside. However, I see from your question in the link above that capacitance might be affecting your circuit more than on-resistance.

    If you want to keep the same level of switch density, you could have a look at the ADG5434, lower on-capacitance with a higher on-resistance. Looking at 16 SPDT switches in parallel, the highest capacitance you would then see is 809 pF compared to 1092 pF in the ADG1434.

    The ADG5436F would have capacitance lower than both ADG1434 and ADG5434, with a resistance lower than the ADG5434, but with only 2 SPDT switches per IC.

    For your voltage range, a pulse of +/-3.5 V through the switch, I recommend that you look at the ADG1634, which has the same density as the ADG1434, similar on-resistance as well, and lower capacitance. The caveat is the supply voltage that should be between +/-3.3 V to +/-8 V, and not +/-15 V. Besides, the ADG1634 on-resistance flatness is higher than the ADG1434 and you might want to consider this in your circuit.

    For the SPICE models, the models that users can download from our Switches and Multiplexers product pages vary from our LTspice models. The SPICE models in the product pages are designed to work in major SPICE simulators, including LTspice. Thus, a few compromises were made to guarantee an operational device across different software.

    Our LTspice switch models have more parameters included in the model and higher accuracy than the .CIR models, however, we still do not include the exact value of capacitance as shown in the datasheet. We do, however, guarantee that all of our switches' AC parameters are modelled, as well as the on-resistance waveform seen in the datasheet.

    Yours sincerely,

    Igor Ono.