Real-time clock options (SBC Lynx)

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SBC Lynx-top.png Applies to SBC Lynx

Introduction

This article describes the options available for the real-time clock (RTC) implementation on SBC Lynx.

i.MX6UL's native RTC (default option)

The default option is based on i.MX6UL's native RTC. The simplified block diagram of this solution is depicted in the following image.


Default RTC implementation


When the system is powered on, the battery is being recharged.

When the system is powered off, on-board battery powers SNVS domain of i.MX6UL processor that includes native RTC. Under these conditions, the typical current drawn from the battery is 100 uA. In case a 17 mAh battery is used (i.e. Panasonic ML-1220/V1AN), battery life is about 170hours.


This solution is quite simple and cheap. However, the timekeeping operation time is relatively short. In case a longer timekeeping operation time is required, it is possible to not populate the on-board battery and to connect a bigger one to the connector J56. For more information, please contact Sales department.

ST M41T83 (alternative option)

This option is based on ST M41T83 RTC. The simplified block diagram of this solution is shown by the following image.


Alternative RTC implementation


Typical current drawn from the battery is 370 nA, when the system is powered off [1]. Thus expected battery life is about 5 years, in case a battery with nominal capacity of 17 mAh is used.

This solution is more expensive but guarantees a longer timekeeping operation time, because M41T83 power consumption is very low. In any case, it is possible to not populate the on-board battery and to connect a larger one to the connector J56 to achieve an even longer operation time. For more information, please contact Sales department.


[1] This consumption largely varies depending of RTC configuration. This figure refers to the configuration detailed in the following registers dump:

tenths: 0x47
seconds: 0x22
minutes: 0x45
hours: 0x11
day: 0x02
date: 0x17
month: 0x01
year: 0x17
calib: 0x80
WD: 0x00
alm1: 0x40
alm1: 0x00
alm1: 0x00
alm1: 0x00
alm1: 0x00
flags: 0x04
timer: 0x00
timerctl: 0x03
ancal: 0x00
square: 0x10
alm2: 0x00
alm2: 0x00
alm2: 0x00
alm2: 0x00
alm2: 0x00
RAM: 0x00
RAM: 0x00
RAM: 0x00
RAM: 0x00
RAM: 0x08
RAM: 0x00
RAM: 0x00
RAM: 0x89