topic Re: SD Power Enable in i.MX RT Crossover MCUs

SD Power Enable

vonp — Wed, 15 Jan 2020 21:47:55 GMT

Hi,

I have a custom board based off of the RT1064-EVK. I am having issues resetting the SD card VDD using M12 GPIO_AD_B1_03 and a simple p-channel mosfet in a high side switch configuration. I have tested this circuit with a restive load at around 300mA with the SD card removed and it works fine. However, when the SD card is inserted and I pull M12 low I measure about 2.3V DC. It seems that there is some leakage current from the SD card IO pins back on VDD. I have compared this to the EVK which does not show this error(unless the SD data lines are driven high then I do, but not in the SD driver demo example). Is there anything I am missing? Why can I not drive VDD low?

Re: SD Power Enable

jingpan — Fri, 17 Jan 2020 05:42:58 GMT

Hi Heath,

You schematic looks fine. I also test on my EVB. When GPIO_AD_B1_03 output 0, SD card VDD is also 0. Did you measure Q1 gate voltage?

Regards,

Jing

Re: SD Power Enable

vonp — Tue, 21 Jan 2020 21:06:39 GMT

Jin,

Yes, I checked the gate voltage on Q1 and looks correct. Like I said above if the SD card is removed Q1 operates as it should, I have also only connected VDD and VSS on the SD card and it operates correctly, but once I connect the data pins it reads VDD at 2.4VDC when off and 3.3VDC when on.

Re: SD Power Enable

vonp — Tue, 21 Jan 2020 21:11:11 GMT

Update:

I found this issue because I was having issues with the sd at boot(some cards would work and others would not). However, I recently updated to the newest SDK_2.7.0_EVK-MIMXRT1064 and it seems to fix the original problem I was having, but I am still seeing some leakage back on VDD.

Re: SD Power Enable

jingpan — Wed, 22 Jan 2020 06:47:04 GMT

Hi,

Yes, it seems the voltage comes from SD card data pins.

Regards,

Jing