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ADS8688A: ADS8688A evaluation data

Deva Kumar
Prodigy 20 points
Part Number: ADS8688A


Sir,

1. Please find attached ADS8688A data tested on our evaluation pcb. When input to ADC is increasing the error of the ADC is increasing. Pls suggest.

2. Provide the data captured with TI evaluation pcb.

3. In ADS8688A, –3-dB cutoff frequency for the antialiasing filter is typically set to
15 kHz. I require a cut off of 50Hz. Pls suggest.

4. In ADS8688A, it is mentioned - Use these Over voltage protection circuits as a secondary protection scheme to protect the device. I need over voltage protection circuit in my pcb. So If I use ADS8688A, does it mean I still need to provide over voltage protection circuit at input of ADS8688A.

5. Iam looking for multichannel data acquisition ADC at least 8 channels or more, with input voltage range of +-10V. Sampling rate at least 100 ksps. Please suggest. 

ADC-evaluation_data1.xlsxthank you

Deva kumar

  • 0
    TI__Mastermind 25030 points

    Hello,

     1.  You test data is a good way of testing for functionanyly of the device, but it does not reflect linearity of the device. Forr linerality testing, you will need to look at the DNL and INL of the device. I found two would documents to show this, one through TI and a Univeristy that goes deeper into the math, and another that is a higher level academic explanation.

    I would also suggest looking at Precision Labs, section 3, to learn more about offset and gain calibration after lineraty.

    2. In the softwre GUI, that can be downloaded here  you can access real data. Withing the GUI, without connecting the EVM, you can enter simulation mode. The simulation data is real data collected using the EVM.

    3. The internal filter is not programmable, thus if you would like a filter at 50Hz, you will need to add an external RC filter in the input circuit. One way of implementing an external RC filter is usning the layout shown below, where R would be the filter resistor.

    4. This devie is commonely used in grid infrustrutcor, thus the datasheet was somewhat catered to these types of applications that has probability of high voltages. If you suspect your application will need protection above what the device can handle then you should also add external primary protection.

    5. I did a quick parametric search based on your requirements, and came up with 8 devices, which will all be very similiar. If you are able to share more detail about your application, it would be easier to give a better suggestion

    Regards

    Cynthia