When the system enters into deep sleep mode, current can leak from i.MX6 IO pins if the pin status does not match to the status at the other ends.
(i.e. i.MX6 pin status is HIGH but the external status is LOW or vice reverse). Current can be saved if the the pin status when suspend are matched. This is especial important to the eReader application because the deep sleep mode spans most of the battery lifetime.
On i.MX6SL EVK when suspend, the current input at the (VDD_SNVS_IN + VDD_HIGH_IN) 3.1 V power rail is ~400uA . By applying the software change here to match the IO pin status, this current can reduce to ~180uA. Please refer to the comments in the attachment for the detail.
Here is my measurement result from a i.MX6SL EVK Rev B.
| Supply Domain | Voltage (V) | P(mW) | I(mA) |
| VDD_ARM_IN | 0.983 | 0.022609 | 0.023 |
| VDD_SOC_IN + VDD_PU_IN | 0.983 | 0.81589 | 0.83 |
| VDD_HIGH_IN + NVCC33_IO | 3.16 | 0.59724 | 0.189 |
| VDD_SNVS_IN | 3.1 | 0 | |
| Total Power (exclude NVCC_DRAM + LPDDR2) | | 1.435739 | |
Please notice that additional current can be saved on i.MX6SL EVK if:
1. KEY_COL4 and KEY_COL5 pins are controlling the USB 5V power for OTG & host operation. These pins have external 47K pulldown. When suspend, pin KEY_COL5 is always HIGH to keep the USB 5V at the HOST port. Power can be saved if kernel option CONFIG_USB_EHCI_ARC_H1 is not enabled (no usb function at HOST port) or the USB-HOST 5V power is turned off when suspend.
2. When SD card is present at any card slot, the CD connection at the slot will be mechanically shorted to GND. It is because the CD pin has internal 100K pullup, 31uA will leak. This leakage can be saved if the the SD/MMC media is hardwired to i.MX6SL without card detect pin.
3. ECSPI2_MISO, ECSPI2_MOSI, ECSPI2_SS0 pins are configured as input with 100K internal pullup for i.MX6SL to communicate with the charger MAX8903B. It is because the charger's CHG_DOK pin is always asserted on the EVK, the ECSPI2_MOSI is always LOW all the time and the system is leaking 31uA here. Power can be saved if the system do not need to monitor this pin.
Original Attachment has been moved to: ENGR00267271-1-mx6sl-minimize-the-VDDHIGH_IN-current.zip
