i.MX 7Dual NVCC_XXX power usage on DSM

[falstaff]

Hello,

We currently measure about 75mW on a i.MX 7Dual in DSM with NVCC_XXX/VDD_USB_OTG1_3P3_IN/VDD_USB_OTG2_3P3_IN on (3.3V). When we turn off the rail, we measure around 42mW. What are the expected power requirements on those rails? We depopulated external components and set all GPIO pins to input/100k pull-downs, yet the rail seems to consume about 33mW...

A second issue, when we turn off the NVCC_XXX rail via PMIC sleep mode (e.g. configure the rail to be turned off when PMIC_STBY_REQ is issued) the system immediately deasserts PMIC_STBY_REQ as soon as 3.3V goes low (see attachment). The system then waits in a intermediate state consuming around 135mW. Then, some time later when the wakeup source (RTC) triggers, the system resumes fine. We have no GPIO configured as wake-up source (also all GPIOx_IMR registers are 0, and manually masked all interrupts sources using GPM_IMR (via imx_gpcv2_mask_all). What can cause that wake-up?

Best regards,

Stefan

[jamesbone]

Hello Stefan,

Recently NXP Apps team  found the USB PHY will take higher current consumption in DSM mode, and it can't be turns off by SW. So, we suggest add external power switch (MOSFET) to turns off the VDD_USB_OTGx_3P3_IN in DSM mode.

(In case the USB OTG port is not using, you can connect VDD_USB_OTGx_3P3_IN and VDD_USB_OTGx_1P0_CAP

to GND to reduce the power consumption

The ADC port may take higher current consumption in DSM mode even it is not using

 Turns off the Digital power rails (NVCC_xxx) in DSM mode is not allow, please keep the digital power rails on.

The second issue may cause by the NVCC_xxx power off, please check it again. 

Best Regards,

Jaime

[falstaff]

Hi Jaime,

Thanks for your answer. We do use USB, so connecting the rails to ground is not an option for us. Do you have an estimate how much the USB PHY take during DSM?

jamesbone wrote:

Turns off the Digital power rails (NVCC_xxx) in DSM mode is not allow, please keep the digital power rails on.

The second issue may cause by the NVCC_xxx power off, please check it again. 

Table 14 in the current Datasheet (IMX7DCEC, Rev. 3 01/2017) says one can turn off NVCC_xxx, in low power mode and even in run mode (with the comment "The NVCC_XXX can be off in RUN mode / Low Power mode if all the pads in that IO bank is not used in the application, the NVCC_XXX supply could be tied to GND.").

We have the USB PHY and the NVCC_xxx rails on a single switchable power rail...

Best regards,

Stefan