ADA4932 Vocm and SPICE model issue

Hi,

I imported the ADA4932.cir into LTSpice and I am using it to design a single-ended-to-differential level-shifted ADC driver for the AD9257.  I use a single-ended 5V supply and just put in 0.9 V for the Vocm.  However, the AC analysis shows the circuit is completely broken.  Only a Vocm of 2.5 will work with the circuit.  Am I modeling this wrong?

Thanks.

Here is the circuit:

Parents
  • +1
    •  Analog Employees 
    on Feb 4, 2019 2:02 AM

    Hi buckd,

    ADA4932's Vocm is specified to be −VS + 1.2 to +VS − 1.2 when operating at Vsy=5V. This will translate to 1.2V to 3.8 V operating range. With that being said, Vcm=0.9V will definitely won't work.

    Regards,

    Jino

Reply
  • +1
    •  Analog Employees 
    on Feb 4, 2019 2:02 AM

    Hi buckd,

    ADA4932's Vocm is specified to be −VS + 1.2 to +VS − 1.2 when operating at Vsy=5V. This will translate to 1.2V to 3.8 V operating range. With that being said, Vcm=0.9V will definitely won't work.

    Regards,

    Jino

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