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i.MX28 with external power supplies

Question asked by garyaylward on Oct 24, 2012
Latest reply on Jan 23, 2013 by fang mei
Branched to a new discussion

Does anyone have any experience of using the iMX28 without using the PMU?


Doubtless this seems like a strange request, but we need to dramatically reduce the capacitance on our board; having 33uF on every power rail is causing real headaches. So the plan is to use external DC/DC converters with much higher switching frequencies and hence smaller decoupling capacitors.


I have read AN4199 but it is only of limited help as it always assumes that the PMU will be used, and simply says 33uF is needed on each power rail (even if the LDOs are used instead of the DC-DC converters?)


So has anyone managed to ignore the PMU completely?

Does the iMX28 work if you just apply the correct voltages to VDDD, VDDIO_33, VDDIO_18 and VDDIO_EMI in the correct sequence?

Will it work with smaller bulk capacitors, assuming the DC-DC converters only require a couple of uF to drive a 600mA load?


Any suggestions/experiences gratefully received!