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Original question:

ADS8588H: External ADC

ADS8588H: Need OPAMP BUFFER for ADS8588H

Ramesh Palanisamy
Intellectual 620 points
Part Number: ADS8588H
Other Parts Discussed in Thread: OPA365, OPA836, ADS8528, ADS8568, ADS8568EVM-PDK

Hi TI experts,

I am looking for a suitable OPAMP buffer for ADS8588H with input voltage range +/- 10V.

For other details & requirements about ADS8588H,pls refer the following thread which i already posted.

https://e2e.ti.com/support/data-converters/f/73/p/725867/2691426?tisearch=e2e-sitesearch&keymatch=ADS8588H#2691426

I understand from the following link for selection guidelines of OPAMP buffer for ADC.

https://www.changpuak.ch/electronics/Choosing_OPAMP_to_drive_ADC.php

Pls suggest a suitable OPAMP buffer with higher CMRR,higher bandwidth & +/-10V operating range.

I have located some options like OPA365,OPA836,TLO84 etc.

But none of above are satisfying my requirements to meet +/-10 V input range.

Kindly held me to locate right OPAMP BUFFER for the selected ADC - ADS8588H.

regards,

Ramesh P

  • 0
    TI__Guru**** 181351 points
    Hi Ramesh,

    Can you tell us a little more about the sensor you are trying to interface with? The ADS8588H has a high impedance input network and does not necessarily need the same drive requirements as described in the 'Choosing OPAMP to drive ADC' documents you are referring to.
  • 0 in reply to Tom Hendrick
    Intellectual 620 points

    Hi Tom,

    Wish U a happy New year 2019.

    Actually,the ADC ADS8588H is intended to be used for power electronics application (DC-DC Converter & DC-AC inverters).

    We need to sense high frequency current signal of 50 kHz to 100 kHz from which common mode noise needs to be eliminated.

    I believe that the CM noise will be eliminated with the help of opamp buffer stage with high CMRR & higher bandwidth.

    Pls go through the datasheet of current sensor P/N :  LA100-P from the below link.

    http://www.europowercomponents.com/media/uploads/la100-p.pdf

    Please let me know whether i can use simply anti-aliasing RC filter only to remove noise at the input of ADC (or) should i include opamp buffer(voltage follower) at the ADC i/p?

    regards,

    Ramesh P

  • 0 in reply to Ramesh Palanisamy
    TI__Mastermind 45955 points

    Hi Ramesh,

    As Tom mentioned, ADS8588H has a high impedance input network and does not necessarily need the same drive requirements as the web link. Since your input signal frequency is 50kHz to 100kHz which is higher than signal bandwidth of ADC's internal analog filter 24kHz(+/-10V range), so your signal will be attenuated and data acquisition will be affected. An ADC without internal filter limitation can be used for your application based on your sampling rate and other requirements.

    Thanks.

    Best regards

    Dale

  • 0 in reply to Dale Li
    Intellectual 620 points

    Hi Dale,

    Thanks for your inputs.

    As you have mentioned ,ADS8588H has limitation due to limited bandwidth of internal analog filter.

    So,i have chosen ADS8528 according to my requirement. Pls refer to the datasheet for the same.From the page Nos (42) & (43)-

    it is clearly mentioned about interfacing opamp stage,filter with ADC input. But still,i need to confirm about the following since it is required to measure high frequency signals.

    Actually,the desired switching frequency of my converter is 25 kHz ,as a starting point.

    It may be increased to 50 kHz later.I understand from the datasheet  - ADS8528 has 48Mhz bandwidth.

    Is there any other issues while using ADS8528 or ADS8568 for my application?

    Pls confirm.

    regards,

    Ramesh P

  • 0 in reply to Ramesh Palanisamy
    TI__Mastermind 45955 points

    Hi Ramesh,

    When designing the driver circuit with amplifier to drive ADS8568, please follow up the design procedure in Precision Labs to select proper amplifiers and external passive components, '5. SAR ADC Input Driver Design' of the web link as below:

    https://training.ti.com/ti-precision-labs-adcs

    Also, you can get a ADS8568EVM-PDK for experiments with proper amplifier and components before you make your own hardware.

    Thanks.

    Best regards

    Dale