• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 46 subscribers
  • Views 976 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADS1018: I/O Leakage questions

Shawn Workman
Genius 14200 points
Part Number: ADS1018
Other Parts Discussed in Thread: ADS1118

There is a concern with the digital I/O leakage current on the ADS1018, which is rated at -10 to 10uA.

 

1.)     Is the I/O leakage on the ADS1018/ADS1118 really +/-10uA?

2.)     Is the leakage still present in the single-shot mode automatic shutdown scenario?

3.)     Also, if the mux input is not activated, is the leakage still present or do all the pins leak (+/-10uA) whether they are actively connected to the mux/PGA regardless? Times four inputs the digital I/O could be up to 40uA if all the I/O leak regardless?

  • 0
    TI__Guru* 93765 points
    Shawn,


    Here are some answers to the ADS1018 questions.

    1. The I/O leakage is specified to ±10uA as a maximum, but it is significantly less than that. Looking at some data of 30 units, it shows that leakage goes from about 0 to 30nA over temperature. However, all of the variation is likely due to test repeatability. I believe that the reason for the large specification is that we didn't want to use the extra test time to measure such a low current.

    2. It's likely that the leakage is the same regardless of the device state. It'll be the same regardless if the device is in continuous conversion mode, or powered down after a single shot conversion.

    3. The mux leakage may have a small amount of contribution, but it is likely that the leakage is due more to the ESD structures on the pins of the device. These devices are much larger than the devices use for the input multiplexer. Note that for the analog input pins, there may be an input current that isn't described as leakage. This would be the input impedance of the ADC, which depends on the input voltage and the PGA range setting of the device. Common-mode and differential input impedance are described in the Electrical Characteristics table in the datasheet on page 6 (and also described in the text on page 12).


    Joseph Wu
  • 0 in reply to Joseph Wu
    TI__Genius 14200 points
    So are the ESD structures on all of the input pins and would the leakage be 30nA times four inputs?
  • 0 in reply to Shawn Workman
    TI__Guru* 93765 points
    Shawn,


    Yes, the ESD structures are on all the of the input pins and combined you would have 4x that current coming out.

    Again, I'd say it's likely that the real input current is under 10nA (without counting the input impedance) and that the wide variation in the measured input current is test repeability.


    Joseph Wu