TMS570LS0914: ADC-input-leakage

user6353118

Hi E2E,

me and my team are using the ADCs for several voltage measurements and we want to determine the accuracy of our system based on component tolerances, leakages, etc.

The datasheet seems to show that the leakage current is equivalent to current sources parallel to the inputs:

Table 7-24 gives us a value for the leakage current which we should expect in our system:

Do these values refer to a certain range of values for Rext and Cext?

Do large values of Rext necessicarly lead to a larger error due to the leakage current beeing constant, regardless of source impedance at the input?

Is the leakage constant or does it change dependend on the source impedance?

Hope you can help us out.

Thanks and best regards,

David

over 5 years ago

0 Sunil Oak over 5 years ago

TI__Mastermind 49120 points

David,

The input leakage is not dependent on the impedance of the external circuit connected to the input. Rather it is dependent on the actual level on the input channel, as described in the datasheet table. If the input levels are "away" from the extremes of VSSAD and VCCAD the input leakages are lower (and the ADC accuracy is better).

0 user6353118 over 5 years ago in reply to Sunil Oak

Prodigy 50 points

Hi Sunil,

Lets say VSSAD=0 and VCCAD=3.3V. For a rough estimation of the leakage, can I assume that I_AOSB=-2µA at 0V input level and 4µA at 3.3V input level?

Thanks and regards,

David

0 Sunil Oak over 5 years ago in reply to user6353118

TI__Mastermind 49120 points

David,

With the input levels close to the VSSAD and VCCAD supplies, you are looking at worst-case leakage conditions. I have highlighted the datasheet specifications that apply in these cases.

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TMS570LS0914: ADC-input-leakage