AN4199 - VDDA

[thrtn]

AN4199 says, "By default, VDDA and VDD1P5 are set to 1.8 V and 1.5 V, respectively, and they should not be changed.", but IMX28CEC says VDDA can be set up to a max of 2.1V. Which is it? If VDDA can be changed, is there a special set of steps one must take to change it? Thanks!

Message was edited by: Triana Horton

[gusarambula]

Hello Triana Horton,

Both statements are correct. The default value for VDDA is 1.8V. However, there is a minimum and maximum range that VDDA can withstand, this is the parameter shown on the Datasheet. The VDDA minimum value is 1.62V and the maximum 2.1V; while the ideal scenario is for it to be 1.8V there is a margin in which it will work as expected.

I hope this information is what you were looking for!

[thrtn]

Yes, I understand that, but I'm not sure how both of those statements can be correct. Either you can't change it or you can. Why does the reference manual make it a point to note these 2 rails, but not the others that can be changed? What effect does it have on the system to change these two?

[gusarambula]

Hello Triana Horton,

It is recommended not to change these supplies even tough there is a range in which the system will work and you may take advantage of this. For example, you may set VDDA to 1.75V to minimize power consumption. However, there are other variables to consider like VDDA providing power to a DDR2 that works at 1.8V.

Unfortunately there is not a lot of information on the direct consequences on power consumption or effects on the different modules depending on the configuration of these supplies. The recommendation is using them on the values specified.