3.3. RTC & Power-Button

Pin Signal Description type I/O
13 VBACKUP DS1339 RTC backup power supply. Supply voltage must be held between 1.3V and 3.7V for proper RTC operation. This pin can be connected to a primary cell such as a lithium button cell. Additionally, this pin can be connected to a rechargeable cell or a super cap when used with the trickle charge feature. Refer to DS1339 datasheet for details. power I
Module Remark
TX25 Connected to BAT_VDD DRYICE backup power supply input, max. 1.55V The i.MX25 internal RTC is not supported
TX6 without DS1339 i.MX6 RTC backup power supply. Supply voltage must be held between 2.9V and 3.3V for proper RTC operation.
14 PMIC_PWR_ON PMIC dependent Function. Leave unconnected if not used.   I
Module Remark
TX25 No PMIC onboard - Not connected
TX28 PSWITCH - Used for chip power on or recovery. PSWITCH is at MID level by default. Refer to i.MX28 reference manual for details.
TX27, TX51 This is an active high push button input which can be used to signal PWR_ON and PWR_OFF events to the CPU by controlling the PMIC EXT_WAKEUP. Refer to LP3972 datasheet, page 49 for details.
TX48, TX53 Connected to LTC3589 WAKE. To power down, drive this pin LOW. Refer to LTC3589 datasheet, page 29 for details.
TX6 Connected to PMIC ON. Refer to PMIC datasheet for details.
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