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TMS320F280049: PGAs in the 280049 DSP

Leo Smith57
Prodigy 320 points

Part Number: TMS320F280049

Does TI have a model for the PGAs in the 280049 DSP?  There is an IBIS model for the DSP on ti.com, but I read the file and I don’t think there’s anything about the PGAs in there.  I’m talking about with pF of capacitance on the scaling network and things like that.  Is the op-amp the same as something TI makes in a discrete package (such that it would have a lot of info regarding the op-amp itself)?

  • 0
    TI__Mastermind 28275 points
    Hi Leo,

    If you are referring to the input model of the PGA, we don't provide one. However, the PGA was designed to work well with the internal ADC. You should use the ADC input model in addition to the information provided in the PGA chapter "Analog Front End Integration". You can find the PGA specification in the data manual.
  • 0 in reply to Frank Ankapong
    TI__Prodigy 320 points

    When using remote ground sensing it is not useful and it moves about 10-20mV with respect to ground while you are measuring a 10mV differential signal, you can see how the signal can get overcome by the noise.  Actually, it works pretty well when you directly connect the shunt to the PGA inputs.  But adding an offset as in Figure 14-8 is not as simple as portrayed when using the PGA as a differential amp. Thus the need for the input model. 

  • 0 in reply to Leo Smith57
    TI__Mastermind 28275 points
    PGA_GND connected to your signal ground should give you the best performance possible. If you are seeing poor performance with that topology, it most likely points to your signal and ground not being routed in parallel and close together. The principle behind that is, if your signal and ground are routed close to each other, an injected noise will have roughly the same profile on both signal and ground so they should cancel each other.

    Not sure what a PGA input model has to do with this.
  • 0 in reply to Leo Smith57
    TI__Mastermind 28275 points
    Leo,

    Do you have any further questions on this?