Real-time clock options (SBC Lynx)
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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.
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.
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
