2387736_en-US

[#1]

RT1180 VDDA_ADC_1P8 source

Hi,

In RT1180 reference manual, VDDA_ADC_1P8 source is different between Figure 70. Power Architecture (§19.3.2) and Figure 90. Power system overview (§24.3.2.1): it is respectively connected to VDD_AON_ANA or DCDC_1P8.

Which source is it preferable to use?

Regards

Rémi

Re: RT1180 VDDA_ADC_1P8 source

Hi @rémi,

According to the hardware design guide, it is recommended to avoid using the internal DCDC/LDO output as the ADC reference and instead use a more accurate external voltage reference.

If you prefer to use an internal reference, I recommend VDD_AON_ANA. Alternatively, you may use an external reference for VREF, the EVK implements both options.

Best Regards,
Pablo

Re: RT1180 VDDA_ADC_1P8 source

Hi @Pablo_Ramos ,

Thanks for your feedback, 

Sorry I made a typo in pin name, you should read:

In RT1180 reference manual, VDDA_1P8_IN source is different between Figure 70. Power Architecture (§19.3.2) and Figure 90. Power system overview (§24.3.2.1): it is respectively connected to VDD_AON_ANA or DCDC_1P8.

Which source is it preferable to use?

Regards

Rémi

Re: RT1180 VDDA_ADC_1P8 source

Hi @rémi,

In the case of VDDA_1P8_IN, I recommend referring to the EVK design schematic, which uses VDD_AON_ANA or an external reference to power VDDA_1P8_IN.

Best Regards,
Pablo

Re: RT1180 VDDA_ADC_1P8 source

Hi @Pablo_Ramos ,

Thanks for your feedback.

Is there any technical explanation in hardware design guide or any other NXP documentation to justify using VDD_AON_ANA or an external reference to power VDDA_1P8_IN rather than DCDC_1P8?

Regards

Rémi

Re: RT1180 VDDA_ADC_1P8 source

Hi @rémi,

Both connections are correct. However, the Hardware Design Guide mentions that for details on power domains that are not described in Figure 1. Power Control Diagram, you should refer to the MIMXRT1180-EVK design schematic.

In the EVK schematic, VDDA_1P8_IN is powered from the same source as VDDA_ADC_1P8, which provides the option of using either an external reference or VDD_AON_ANA. This is the basis for my previous recommendation.

Best Regards
Pablo