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ADS1220: SMPS noise concern

JAP
Intellectual 2410 points
Part Number: ADS1220

Dear Experts,

If ADS1220 is powered from SMPS, how big of a concern the switching noise from SMPS is? Should there be any differences in performance when compared to ADS1220 + LDO?


Thanks!

Rgds,

Juha

  • 0
    TI__Guru** 113765 points

    Hi Juha,

    Not all switchers are the same.  Some switchers are much noisier than others, the switching frequency can vary and noisy supplies can impact the performance of the ADC.  At a gain of 1 with the internal reference, the ADS1220 is trying to resolve to about 244nV.  I've seen switcher outputs with 100's of uV of noise.  Also, depending on efficiency and loading, the output voltage can vary.  This variance needs to be considered as an error with respect to the PSRR of the device.  So to get high levels of performance we suggest using an LDO to clean up the switcher. If a switcher is to be used then the switching frequency should not be a multiple of the modulator frequency of the ADS1220 (256kHz) to help prevent the switching artifacts from aliasing back into the passband.

    Best regards,

    Bob B