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Spice model behavior for ADA4930

Category: Software
Product Number: ADA4930
Software Version: LTSPICE XVII

Hi, I'm running simulation for ADA4930 model already available on LTSPICE (XVII). The purpose is to feed differential output to ADC, AD9250, that supplies the Vocm of 0.9V.

The scheme is just single input sinus of 2Vpp, 5V supply, 0.9Vocm, gain G=1 with Rf and Rg = 301ohm, and no input impedance matching for now in order to simplify the analysis. I get the following :

I got the following, in red Vin=2Vpp, blue Vout+ and in green Vout-.

I don't understand why Vout+ and Vout- are clipped at Vout+min = 0.6V and Vout-max = 1.2V. The output range from the datasheet is well between the 0,18V to 3.38V output voltage min and max voltages recommended, Vpp max is 2V, and Vocm must be between 0.3 and 2.8V.

So to me here everything should be ok, why are these outputs clipped ?

Thanks

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  • Hi Gilbeys,

    My bad I really thought I shared the schematic, here it is :

    I believe the /SHDN should be set high in order to enable the aop, that is why you got a voltage amplitude much smaller while the gain is set to 1.

    Can you try again to see if the output is clipped ? I suppose this might be due to model inaccuracy because I don't see why negative voltage wouldn't be allowed !

    Regards,

Reply
  • Hi Gilbeys,

    My bad I really thought I shared the schematic, here it is :

    I believe the /SHDN should be set high in order to enable the aop, that is why you got a voltage amplitude much smaller while the gain is set to 1.

    Can you try again to see if the output is clipped ? I suppose this might be due to model inaccuracy because I don't see why negative voltage wouldn't be allowed !

    Regards,

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