About MPC8548E Power Sequencing

youngho_cho — Tue, 09 Jul 2019 09:26:36 GMT

Hello, I'm Youngho.

I want to know power sequencing of MPC8548E.

According to its datasheet, MPC8548EEC, power sequencing is just 2 steps as follows:

1. V_DD, AV_DD_n, BV_DD, LV_DD, OV_DD, SV_DD, TV_DD, XV_DD.

2. GV_DD.

And, the NOTE is as follows:

Note1: Items on the same line have no ordering requirement with respect to one another. Items on separate lines must be ordered sequentially such that voltage rails on a previous step must reach 90% of their value before the voltage rails on the current step reach 10% of theirs.

Note 2: In order to guarantee MCKE low during power-up, the above sequencing for GV_DD is required. If there is no concern about any of the DDR signals being in an indeterminate state during power-up, then the sequencing for GVDD is not required.

Note 3: From a system standpoint, if any of the I/O Power supplies ramp prior to the V_DD core supply, the I/Os associated with that I/O supply may drive a logic one or zero during power-up, and extra current may be drawn by the device.

As I understood above, power sequencing is that the core powers is first powered up and then the I/O powers is next.

So, power sequencing I thought is as follows:

1.V_DD

2.AV_DD_n, SV_DD, XV_DD

3.BV_DD, OV_DD, LV_DD, TV_DD

4.GV_DD

Am I right?

Re: About MPC8548E Power Sequencing

r8070z — Wed, 10 Jul 2019 15:24:16 GMT

Have a great day,

For sure V_DD to AV_DD_n delay is not required. Typically AV_DD_n is V_DD applied via PLL Power Supply Filter Circuit (see MPC8548E PowerQUICC III Family Bring-Up Guide). IO power should be delayed if any IO pin associated with it can harm system f.i. due to contention. I think the serdes io pins are quite harmless. In any case your power sequence is correct too if all supplies reach their stable values within 50 ms.

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About MPC8548E Power Sequencing

Re: About MPC8548E Power Sequencing