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ADS8598H: Voltage Reference Selection

Mahabir Prasad
Intellectual 300 points
Part Number: ADS8598H
Other Parts Discussed in Thread: REF5025, REF6025, REF6225

Dear Members,

I am designing with ADS8598H (seismic application, Delta-Sigma are not suitable due to some technical reasons) with folllowing options (long term stability, low noise, low drift are the main points for design). The application has temperature range of -10 degree to 60 degree. Need help for selection of voltage reference type and part.

1. Internal or external Voltage Reference

2. If external, REF6025 adn REF5025.

Before closing the hardware design, I want to finalise above to have minimal parts on board.

Q.1 - Selected external reference due to temperature drift poor than external one.Need comment, does it is wise go external instead of internal based on above temperature range?

Q. 2 - External Ref REF5025 or REF6225 ? 5025 does not have output buffer, but has very good source and sink of current 10mA compared to 6225 (which is 4 mA). One parameter is not able to trace in 5025 DS, output impedance? Being such value of source/sink, do we need to know Output Z and buffer at output?

I like to go with REF5025, becuase its input power supply range which is 18V, whereas REF6225 is 5.5V max.

Thanks in advance.

Dr. Mahabir Prasad

  • 0
    TI__Mastermind 39225 points

    Hello Mahabir,

    Thanks for choosing ADS8598H in your design.

    The on-chip reference on the ADS8598H has a good accuracy and drift performance comparing with many individual voltage references in the market, however if a precision reference voltage is expected across the entire temperature range, an external voltage reference can be a good solution because the internal reference of the ADS8598H is only characterized with a typical drift specification.

    The high-grade version REF5025 has a similar performance as REF6025 in terms of initial accuracy, drift and so on, the key difference between them is, the REF6025 integrates a high BW buffer on the output which is very helpful to settle the reference signal when driving a switch-capacitor structure SAR ADC at a higher sampling rate. However, ADS8598H has integrated a reference buffer which can be enabled when an external voltage reference is used. Hence, REF5025 can be directly used for ADS8598H. The REF5025's output impedance should be small since a gain amplifier is used on the output, I don't have a number on my hand but REF5025 has been used on the ADS8588SEVM which is compatible with ADS8598H in the same ADC family, the EVM board has been verified by us, so I do not think there is any potential issue to use REF5025 for ADS8598H. The reference input of the ADC doesn't sink too much current, thus both voltage references can be used at this point.

    I hope this helps.

    Best regards,

    Dale

  • 0 in reply to Dale Li
    Intellectual 300 points

    Thanks.

    After your reply, I am going with REF5025 (High Grade), SOIC package.