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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