i.MX8Mplus NVCC sequencing

[max123]

I am a little confused about NVCC-power-sequencing and using 3.3V and 1.8V for IO.

According to IMX8MPIEC 3.2.1 (Power-up sequence) is NVCC_xxx 1.8V -> NVCC_DRAM -> NVCC_xxx 3.3V.

On a PCA9450CHN, Buck 4 (3.3V) and Buck 5 (1.8V) could therefore be used, since Buck 4 is started after NVCC_DRAM, Buck 5 before.

Why should the sequence for the same voltage change just because 1.8V is used instead of 3.3V? Therefore I think I may be missing something important.

Therefore my question:

Can Buck 4 be used to power some NVCC_xxx voltages with 3.3V, like NVCC_I2C_UART or NVCC_JTAG? Are there any drawbacks of doing so, and is it possible to use both 1.8V and 3.3V? The EVM only uses 1.8V for some reason, which is inconvenient for me in some cases.

[igorpadykov · Accepted solution]

Hi Maximilian

>Can Buck 4 be used to power some NVCC_xxx voltages with 3.3V, like NVCC_I2C_UART

>or NVCC_JTAG?

yes as Buck 4 (3.3V) is started after NVCC_DRAM as you mentioned

>Are there any drawbacks of doing so, and is it possible to use both 1.8V and 3.3V?

no drawbacks as this complies with i.MX8M Plus power-up sequence, NVCC_xxx (1.8 V) -->

NVCC_DRAM-->NVCC_xxx (2.5 and 3.3 V).

> is it possible to use both 1.8V and 3.3V?

yes if it complies with i.MX8M Plus power-up sequence described in Figure 5. The power-up sequence

i.MX 8M Plus Applications Processor Datasheet for Consumer Products

Best regards
igor