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VCO based ADC signal transfer function

mohamin

Hello,

I've implemented a VCO-based ADC in Virtuoso. It consists of a 7-stage ring oscillator. The ring oscillator output phases are sampled with 7bit register and finally the sampled output phases are differentiated by 7-stage differentiator. I attached the schematic of my design. It has a pseudo-differential structure. Each path has a VCO, 1st DFF as a phase sampler and  2nd DFF followed by the Xor is the differentiator. 

Theoretically, VCO must act as a continuous-time integrator. Here you can see a very well-known linearized frequency-domain model of a VCO-based ADC.  

Having had above brief, I want to extract the signal transfer function (Gain and phase Vs. frequency) of the above structure. To be clear, I want to see the low-pass behavior of the VCO (like a continuous-time integrator 1/s), frequency behavior of the differentiator and also frequency behavior of the overall structure (superposition). 

Would you please let me know what kind of simulation I have to do to extract this info from my design in Virtuoso? I am using IC616. 

Many thanks 

Parents

  • I'm afraid I have no experience of this class of circuit (despite having designed lots of ADCs in the past). Others may of course be able to help you, but you may be better off asking this in the analog design board on the  

    forums, which are much more design-centric.

    Regards,

    Andrew.

Reply

  • I'm afraid I have no experience of this class of circuit (despite having designed lots of ADCs in the past). Others may of course be able to help you, but you may be better off asking this in the analog design board on the  

    forums, which are much more design-centric.

    Regards,

    Andrew.

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