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LMP90080-Q1: differential inputs & VREF

Sharan Ghimire
Prodigy 110 points
Other Parts Discussed in Thread: LMP90080-Q1, ADS114S08, ADS1120-Q1

Hello Bryan, 

thanks for that info.

Question regarding 

1) diff analog inputs:

this is something i am planning to use. Do you have any feedback

2)  for the reference voltage, I am planning to tie Vref to VA. The datasheet just says having Vref below VA would have "diminished performance". Can you comment on this?

Thank you.

  • 0
    TI__Mastermind 37591 points

    Hi Sharan,

    Do you have any specific question regarding the differential analog inputs?

    Regarding VREF and VA: using VREF = VA provides the maximum full-scale range possible so you can measure the largest span of input voltages. Moreover, as the datasheet says, reducing the LSB size to a very small value is not necessarily helpful, as the intrinsic ADC noise will start to dominate and you won't actually get the benefit of reduced noise. This is generally true for many ADCs at the 16-bit level, not just this specific ADC. If you want to learn more about ADC noise principles, you can check out our Precision Labs content on ADC noise, module #3: https://training.ti.com/ti-precision-labs-adcs

    In general, if you do not need the automotive grade version of the LMP90080-Q1, I would recommend switching to the ADS114S08. This is the third-generation of the LMP devices, and is better in almost every way: better DC performance, smaller package, lower power, more features, lower noise, lower price.

    If you do need the automotive grade version, I would suggest the ADS1120-Q1. This device is also a generation beyond the LMP90080-Q1, and offers better performance at a lower price point.

    It is not that the LMP90080-Q1 is bad device to choose, just that we have newer, much-improved options offered at lower prices.

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 110 points

    Bryan, 

    As the datasheet lays out for the optimal performance, i would just connect VA and Vref together with of course bypass capacitors. 

    yes I do need an automotive grade and temperature range from -40 to 150C is a must along with 4 differential analog inputs. So the ADS P/N you suggested wont work . Unless you have any  other suggestions beside that?

    In regards to differential analog, I saw somewhere in the forum different design techniques implemented so i was just putting it out there how my connection looked like and was wondering if there any suggested methodology ?

    Thanks

     

  • 0 in reply to Sharan Ghimire
    TI__Mastermind 37591 points

    Hi Sharan,

    If you need an automotive grade 0 device, then the LMP90080-Q1 is the best choice.

    Regarding differential input: if your sensor or load has a differential output then differential inputs are certainly the best configuration to choose. Therefore you won't get any resolution loss converting from differential to single-ended, or vice versa.

    -Bryan