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ADS127L01 - about Simulink model, INL

Ryuji
Guru 20090 points
Other Parts Discussed in Thread: ADS127L01

Hello,

The customer will evaluate the ADS127L01.
Then I got the following questions.
Could you please help us?

(1) Simulink Model
The customer would like to model the ADS127L01.
Could you please share the Simulink Model ?
Or other information(Conversion+Equation)  for  model the ADS127L01. 

(2) INL
The device specification is 5ppm(max) of INL on the condition of LP mode and VLP mode.
Is this mean +/-5ppm （i.e. 10ppm width) ?
Or, Is this 0 to 5ppm (i.e. 5ppm width) ?

Best Regards,
Ryuji Asaka

  • 0
    TI__Guru 66706 points
    Hello Ryuji,

    1. The only model that we have available for the ADS127L01 is the IBIS model under Tools/Software on the product folder. What is it that you needed information on? Are you looking for the transfer function of input voltage vs. output code?

    2. The INL specification is +/- 5ppm max for LP and VLP modes.

    Best Regards,
  • 0 in reply to Ryan Andrews
    Guru 20090 points
    Hello Ryan,

    Thank you for the reply.
    Regarding Simulink model, the customer need the following information.

    The customer is modeling the simulink model as
    1 input -> Conversion delay to the LTI system (for example 1us) -> Transfer function (for example, 1MHz) -> 1 output

    Best Regards,
    Ryuji Asaka
  • 0 in reply to Ryan Andrews
    Guru 20090 points
    Hello Ryan san,

    Could I have the reply please?
    If you need more detail information, please let me know.
    I will check.

    Best Regards,
    Ryuji Asaka
  • 0 in reply to Ryuji
    TI__Guru 66706 points

    Hello Asaka-san,

    I'm still not sure exactly what the customer is asking for. Could you explain the goal of what they are trying to model and why they need to model it?

    If by "conversion delay" the customer is referring to "group delay" (the time between an input sample and its corresponding output code), that specification is given as 42/fDATA.

    Please provide as much detail as you can so that I may help you.

    Best Regards,

  • 0 in reply to Ryan Andrews
    Guru 20090 points
    Hello Ryan san,

    Thank you for the reply.
    I understood about conversion delay.
    Thus, if the fDATA is 512ksps, group delay will be 82.03us on the Wideband filter mode.
    Could you please let me know the calculation example on the Low Latency mode?

    The customer requirement is the following.
    (1) The time between an input samples and its corresponding output code. Thus your understanding about conversion delay is correct.
    (2) And time constant of the (1) answer.

    Best Regards,
    Ryuji Asaka
  • 0 in reply to Ryuji
    TI__Guru 66706 points
    Hello Asaka-san,

    I have asked our designers about the low-latency filter group delay and hope to provide you with an answer shortly.

    Regarding (2), what do you mean by the time constant? Are you referring to the units of the group delay measurement? The units will be in seconds as group delay is inversely proportional to the output data frequency (i.e. x / fDATA).

    Regards,
  • 0 in reply to Ryan Andrews
    TI__Guru 66706 points
    Asaka-san,

    After discussing your questions with a colleague, I believe you might be confusing the internal operation of a delta-sigma ADC with that of a SAR ADC. In a SAR ADC, a specific input sample will appear at the ADC output after some delay - there is a 1:1 ratio there. However, in delta-sigma ADCs, one input sample does not DIRECTLY appear in the ADC output. Instead, the input samples are averaged with previous samples to produce an output. This is known as the oversampling ratio (OSR), where the input-to-output ratio is OSR:1.

    The important detail for our digital filters is that they are linear-phase filters, which means that signals of all frequencies will experience the same delay through the filter.

    I'm still not clear what you are asking with regards to the "time constant."

    Regards,
  • 0 in reply to Ryan Andrews
    TI__Guru 66706 points
    Asaka-san,

    The total settling time is given for the low-latency filters in Table 3 on page 30 of the ADS127L01 datasheet. The group delay is only specified for the wideband filters, but note that it is really the total settling time that you care about.

    Regards,