MPC5777C power Up sequence

[puneeth_bheemar]

Hi Team,

We are using MPC5777C controller in our design. we observed there are following requirement of power on/down sequencing based on "AN5268 - MPC5777C Hardware Requirements_Example Circuits (Rev. 0.06 / 2016)" document section "3.4 Power up/down sequencing". 

• The recommended power supply behavior is as follows: Use 25 V/ms or slower rise time for all supplies.
• Power up VDDPMC/VDDPWR, VDDA_MISC, VDDA_EQ, and all VDDEx/VDDEHx supplies first and then power up VDD.
• For power down, drop VDD to 0 V first, and then drop all other supplies. There is no limit on the fall time for the power supplies.

However, in the MPC5777C Microcontroller Data Sheet, we are not finding anything related to the VDD power up post other supplies requirement.

Also, there is similar question in the community (Solved: Re: MPC5777C - Power up sequence - NXP Community,) where problem solved by powering on all the supplies together instead of sequencing VDD later.

Please let us know, still do we need to consider the AN5268 old document guidelines, or we can ignore the power on sequence for MPC5777 and ramp up or down any order.

Thank you,

Puneeth KB

[davidtosenovjan · Accepted solution]

Which mode you are using?

Mentinoed sentence
"Power up VDDPMC/VDDPWR, VDDA_MISC, VDDA_EQ, and all VDDEx/VDDEHx supplies first and then power up VDD. "

is rather related to mode with externally supplied VDD. In case VDD is sourced by internal SMPS/LDO regulator, it is more or less out of user control.

Powering on all the supplies together is correct, there's no harm in that.

In the DS there is a specification related to VDD, indirectly telling VDD is supposed to be powered later.