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ADS1298 Reference Voltage

Pieter Willemen
Prodigy 180 points

Hi Ti,

this could be a silly question, but I need to ask: Why is the minimum reference voltage 2.4V?

Even with the highest reslotion of 24 bit, 1 LSB is still only about 0.5µV. It seems to me, that when you use for example a reference of 0.5V, you can use a lower resolution, which means less power usage, which would probably also decrease the noise. Also, when you work differentially, 0.5V is more than enough for EXG applications.

Pieter Willemen

Antwerp, Belgium

  • 0
    TI__Mastermind 43915 points

    Hi Pieter,

    The internal reference selection is either 2.4V or 4V typical with an accuracy of +/-0.2%. It is important than when using an internal reference that there is 300mV to 400mV buffer between the reference value selected and the power supply voltage. When use with an external reference, the part is designed for a 2.5V reference. Generally, with ECG/EKG applications, the input signal is in the range of 5-50mV with a 300mV electrode offset voltage. With the gain options of the internal PGA and the amplitude of the signal of interest, a 2.4V or 4V internal reference is what is preferred. Is there a specific reason you would like to use a 0.5V reference? If you are trying to avoid using gain options, you should note that if you keep the LSB value at a minimum, the internal noise associated with the converter may begin to play a larger role in your conversion result.

    Regards,

    Tony Calabria

  • 0 in reply to Tony Calabria
    Prodigy 180 points

    Thank you for answering.

    I was just wondering why anyone would ever choose a 4V reference, since it seems way too high, for this application.
    I will just take my 2.4V then.

    Pieter Willemen
    Antwerp, Belgium