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VDDA_ADC_3P3

Question asked by Daniel Haslimann on Dec 30, 2019
Latest reply on Jan 5, 2020 by fangfang

Hello

We are not sure about the VDDA_ADC_3P3 Pin of the RT1062.

On some places in the data sheet, it is noted that the difference to VDDA may not exceed 100mV (4.8.2.1.1). On other places, it is noted that VDDA_ADC_3P3 may not be powered when other SoC supplies are off (4.1.3).

Again in another place (4.2.1.1) it is noted, that this supply is not part of the power supply sequence and may be powered at any time.

 

In the conclusion, does this mean that VDDA_ADC_3P3 needs to be connected to the main VDD (DCDC_IN), over some filter elements, or can it be supplied by an exact 3V3 reference which is enabled after the main VDD has powered up?

The latter variant has big advantages in terms of ripple voltage and exactness of the reference, as VREFH is directly connected to VDDA_ADC_3P3 internally in the RT1062.

This information is crucial to our design, so we would be very glad about a precise answer.

 

Thanks for your reply and best regards,

Daniel

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