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Original question:

TMS570LS0714: ADC self-test issue

TMS570LS1224: Many inputs undeterminded at ADC Self-Test

Timon van der Werf
Prodigy 20 points
Part Number: TMS570LS1224

Tool/software:

Hello,

we have a problem with the self test of the mentioned controller, see table below. My understanding to get a good result is: Vu>Vn>Vd, is this right?

For the input connections I cannot share detailed circuitry, but there are different types of components connected (e.g. relay feedback, resistive devided voltage measurement, RC filtering elements,...).

I want to test longer conversion time, but TBC if this is acceptable from functional/safety perspective.

Any ideas, where the rootcause of these results can be? Too much capacitance at input when getting Vn=0?

Kind regards

  • 0
    TI__Guru 69701 points

    Hi Timon,

    Timon van der Werf said:
    we have a problem with the self test of the mentioned controller, see table below. My understanding to get a good result is: Vu>Vn>Vd, is this right?

    Your understanding is correct, and this should be the basic condition that should satisfy and here is the actual comparison for good result.

    Timon van der Werf said:
    Any ideas, where the rootcause of these results can be? Too much capacitance at input when getting Vn=0?

    I didn't know exact root cause for this issue,

    I am doing further analysis to find root cause.

    --
    Thanks & regards,
    Jagadish.

  • 0 in reply to jagadish gundavarapu
    Prodigy 20 points

    Hello Jagadish,

    thanks for the answer. We could evaluate following results:

    Inputs with Vn=0 had no input signal >GND potential while performing ADC self-test. From my understanding, signal >GND-potential (or ADREFLO) is needed to get "good" as result, otherwise the comparison of the 3 measurements Vn,Vd,Vu is not working.

    The onboard signals are affected by parallel capacitances at the ADC inputs. The sampling time is not sufficient to stabilize the system, when changing capacity and/or sampling time, the result gets "good".

    Kind regards

    Timon

  • 0 in reply to Timon van der Werf
    TI__Guru 69701 points

    Hi Timon,

    Timon van der Werf said:
    From my understanding, signal >GND-potential (or ADREFLO) is needed to get "good" as result, otherwise the comparison of the 3 measurements Vn,Vd,Vu is not working.

    I understood the same.

    To get good result it would always better that input is in between REFLO and REFHI. I am suspecting that in the case of customer it is varying and sometimes it is going to GND and this would lead to the problems in the results.

    --
    Thanks & regards,
    Jagadish.

  • 0
    Prodigy 20 points

    Hello Jagadish,

    In addition, we are experiencing issues sourcing the main 16MHz crystal oscillator from our distributor.

    We have been using an NDK reference, but it has become difficult to find.

    We have identified another NDK reference, NX3225GA-16.000M-STD-CRG-2, but we are still waiting for NDK to confirm its compatibility with the TMS570LS1224 MCU.

    Could TI recommend some 16MHz crystal oscillator references for this MCU that are automotive qualified?

    Thank you for your assistance.

  • 0 in reply to david m
    TI__Guru 69701 points

    Hi David,

    Apologies for the delayed response, i was stuck with other issues in this mean time:

    I found below part number in our schematics:

    Can you check whether this would be helpful for you?

    --
    Thanks & regards,
    Jagadish.

  • 0 in reply to jagadish gundavarapu
    Prodigy 20 points
    jagadish gundavarapu said:

    I found below part number in our schematics:

    Can you check whether this would be helpful for you?

    Hello Jagadish,

    unfortunately , this oscillator is not automotive qualified