This is regarding i.MAX6Q based custom hardware design and this design most similar to Nitrogen 6_Max development board. We are using MTFC4GLDDQ-4M IT micron emmc.
We had an issue with EMMC, VCCQ 1.8V supply and it increases up to 2.3V unexpectedly. And we could recover this happens when EMMC configured via u-boot and come to a certain state(Reset).
There are 2 supplies for EMMC
VCC Supply (3.3V) = NAND interface I/O and NAND Flash power supply.
VCCQ Supply (1.8V) = e·MMC controller core and e·MMC interface I/O power supply.
We are using SD4_DATA signals for DATA signals of EMMC from i.MAX (According to above figure) and for those signals i.MAX power block is NVCC_NANDF which can go up to 1.65V to 3.6V range. And we are giving 3.3V for this block. (But in Nitrogen 6 MAX it is 1.8V)
From i.MAX side processor generates signals in 0V ~ 3.3V range.
From EMMC side the e·MMC controller core and e·MMC interface I/O power supply control 0V ~ 1.8V range.
We think this will make conflict inside EMMC and 1.8V suuply override with 2.3V due to mismatch of I/O signal voltage range from processor side.
Can you give a comment on this ? Does our conclusion correct ? Any other reason to happen this kind of issue ?