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AXEL Lite SOM/AXEL Lite Hardware/Peripherals/Real Time Clock

< AXEL Lite SOM‎ | AXEL Lite Hardware
History
Version Issue Date Notes
1.0.0 Oct 2020 New documentation layout



Contents

Peripheral Real Time ClockEdit

DescriptionEdit

The Real Time Clock interface available on AXEL Lite is based on NXP MMPF0100 PMIC.

The Real Time Clock is kept operative through the AXEL Lite PMIC_LICELL pin (J2.14): the LICELL pin provides for a connection of a coin cell backup battery or a “super” capacitor.

A small capacitor should be placed from LICELL to ground under all circumstances.

For more information about PMIC RTC functionality, please refer to the MMPF0100 datasheet.

PoweringEdit

Real-time clock is integrated in iMX6 processor. As such, it belongs to SNVS power domain. This domain, in turn, is powered by PMIC, via PMIC_VSNSV rail (see also this page). PMIC integrates a sort of switch. When 3V3VIN voltage is applied, this is used to power SNVS domain. Otherwise energy is drawn from coin cell battery - if any - connected to PMIC_LICELL (for more details please refer to [1]).


 
Simplified block diagram of AXEL Lite RTC powering scheme


It is worth remembering that 3.0V lithium batteries are supported and that PMIC_VSNSV voltage range is 2.4 - 3.6V. When AXEL Lite enters RTC mode and 3V3VIN voltage is removed, typical current absorption from PMIC_LICELL pin is about 135uA. This value is relatively high with respect to the typical lithium coin cell battery capacity (10 - 50mAh). It is recommended that system integrator verify that expected battery lifetime satisfies system requirement. If not, the use of an external low-power RTC device should be considered.

Pin mappingEdit

The Pin mapping is described in the Pinout table section


  1. NXP, MMPF0100 - PF0100 Data sheet: Advance Information