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ADS8689: Decoupling capacitor requirement on REFIO pin

Takeshi Sasaki
Expert 4480 points
Part Number: ADS8689

Hi team,

Could you give me comment on following customer questions?

Q1. How large capacitor can the customer select the decoupling capacitor on REFIO pin? The datasheet describes 4.7uF as minimum, and he wants to confirm if there is maximum value.  

Best regards,

Takeshi Sasaki

  • 0
    TI__Mastermind 45245 points

    Hi Takeshi,

    The output impedance of the internal band-gap circuit creates a low-pass filter with the capacitor on REFIO pin to band-limit the noise of the reference, a large value capacitor on REFIO pin can limit more noise from the circuit, however it can make the circuit unstable, also it may affect the signal settling of reference voltage on internal switch-capacitor sampling circuit and affect the performance. A 10uF capacitor was designed for REFIO on ADS8681EVM board and the performance specified in the datasheet was achieved, so either a minimum 4.7uF capacitor or 10uF capacitor on REFIO can work well and will not have any impact to the performance.

    Best regards,

    Dale