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

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Version Issue Date Notes
1.0.0 Oct 2020 New documentation layout

Peripheral Real Time Clock[edit | edit source]

Description[edit | edit source]

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.

Powering[edit | edit source]

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 mapping[edit | edit source]

The Pin mapping is described in the Pinout table section

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