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TINA/Spice/ADS7046: Question about the distortion input waveform by ADS7046

Haoyang Zhang42
Prodigy 180 points
Part Number: ADS7046
Other Parts Discussed in Thread: TINA-TI,

Tool/software: TINA-TI or Spice Models

Dear all,

I am now doing a simulation with TINA. But I found that the first-period input waveform to ADC from a buffer and RC filter is distorted by the ADC which is shown below.

Normally it should be a sin wave, but it is distorted now.  Also, there is a high spike during the first cycle of the output wave of ADC.

Could anyone explain to me what cause these two distortions and how to avoid them in practical circumstance?

Thank you!

Best regards,

HaoyangADS7046.TSC

  • 0
    TI__Intellectual 820 points

    Hi Haoyang,

    Seems like it’s not a device issue.The distortion in VF3 and VF4 first cycle & the spike is due to the simulation option problem.

    Kindly use the option ‘Calculate operating Point’ while running transient simulation, this will eliminate these issues,(result below)


     

    Else as per the test-bench signals, for the op-amp, its Common-mode is near 500mv, whereas if you are simulating it with ‘zero initial condition’ , it will forcefully put 0V everywhere at start and then calculate accordingly. Hence this is appearing as a distortion. (look at VF1 to locate the actual op-amp I/p)

    Similar can be situation for the sampling cap, which needs to be at some other operating point, but is forced to 0V, hence initial spike may appear.

    Test-bench with correct settings is attached.

    ADS7046_Mod.TSC