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ADS8598H: ADS8598H AIN_nGND Input Protection

Anushavan Atanasian
Prodigy 230 points
Part Number: ADS8598H

In my design I'm using 1K resistors in series on both AIN_nP and AIN_nGND inputs along with a small cap as recommended in the datasheet. To get the maximum possible accuracy AIN_nGND will be grounded remotely at the signal side.

I understand that the working signal on AIN_nGND must be in -0.3V to +0.3V range. I'm a little concerned about somebody accidentally connecting AIN_nGND to significantly higher voltage, let say reversing inputs and getting up to 10V on AIN_nGND. Datasheet shows clamp circuits on both inputs, so there is some protection already and 1K resistor would limit the current to 10mA. Is it a good idea to also add two Schottky diodes connected in parallel in opposite directions on my board between AIN_nGND and the board signal ground for an added protection level? 

  

  • 0
    TI__Mastermind 37190 points

    Hi Anushavan,

    Thanks to post a great question here.

    The internal clamp circuit inside ADC is mainly designed to protect ADC from out-of-circuit ESD events, In some cases, these internal ESD protection structures can be used to help and protect against electrical overstress (EOS) as long as the input current can be limited into the range of absolute maximum input current rating(+/-10mA), however this solution is not recommended when the clamp is turned on for longer time and doing this can degrade performance and reliability. In general, external protection components will be required.

    When we select an external protection diode, Schottky diode usually is used in forward condition between input and analog power supply or the ground. ADS8598H has wider input range(+/-10V) and analog power supply is only single 5V, so a bidirectional TVS diode between input and ground is better to protect this ADC from electrical overstress than Schottky diode in this use case. Notice that the capacitance of external diode may have a significant impact on system performance, it's important to select proper current limiting resistor and TVS diode. The key point is to protect the ADC from electrical overstress and have minimal impact impact on system performance.

    We do have a training video series also materials published as Precision Labs ADC on TI.com, please refer to following link to get more details:

    Electrical Overstress on Data Converters

    Please let me know if you have more questions, thanks.

    Best regards,

    Dale Li