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Original question:

external clock of ADS1299

ADS1299: external voltage and external oscillator

Ildar Rakhmatulin
Prodigy 230 points
Part Number: ADS1299

Our team made PCB board for ADS1299, and we used the external oscillator and the external reference voltage. But in fact, the ADS1299 can work with an external oscillator and internal references. For which case need to use the external voltage and external oscillator? 

  • 0
    TI__Guru 57346 points

    Hello Ildar,

    Thank you for your post.

    The ADS1299 has the option to use an internal or external voltage reference, and also an internal or external oscillator. You can use both internal options, both external options, or a combination of internal and external.

    To use the internal reference voltage, you will need to power-down the external reference or disconnect it from the VREFP input pin.

    To use the internal oscillator, the CLKSEL pin must be set to 1 (i.e. pulled up to DVDD). It is highly recommended to disable the external oscillator if it is not used in order to reduce noise coupling.

    Best regards,

  • 0 in reply to Ryan Andrews
    Prodigy 230 points

    Thank you, i khow how to use it,
    only I would like to know, which difference between internal and external, the accuracy of ADS1299will be the same?

    I can not understand which case need to use external oscillator and external reference

  • 0 in reply to Ildar Rakhmatulin
    TI__Guru 57346 points

    Hi Ildar,

    An external reference voltage can provide better accuracy and lower drift than our internal reference voltage. The decision is up to you whether your application would benefit from this increase in performance.

    The external oscillator is useful for synchronizing the master CLK for the ADS1299 with your host processor or with other ADS1299 devices. The frequency tolerance or clock jitter is not critical because the CLK is divided down inside the ADS1299, making the performance less dependent on the original CLK accuracy.

    Regards,

  • 0 in reply to Ryan Andrews
    Prodigy 230 points

    Thank you so much Ryan. 

    Please help me yet with the question in the topic - https://e2e.ti.com/support/data-converters/f/73/t/910972