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tlai4
Novice
1,087 Views

rtc failed on edison

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hi,

In our application on edison , we supply the RTC_PWR(V_VBAT_BKUP) with our RTC_BAT or 3_3VPWR(VSYS).

Actually, it work fine in short time even when i power off the Vsys for a while.

After power off a long time, the date time run to the initial date.

We did some experiment catch the trigger down at RTC_BAT.

It didn't catch anything(means the voltage always high)

Is there any way to find the problem?

Thanks

1 Solution
Sergio_A_Intel
Employee
57 Views

Hi,

The circuit seems to be ok. According to the datasheet those are Zener diodes so the design is correct. That leaves the issue to be most likely power related. Have you seen section 4.13 of the Edison module Hardware guide http://www.intel.com/content/www/us/en/support/boards-and-kits/000005808.html Compute Module Hardware Guide for Boards and Kits? There you'll see:

The PMIC can be programmed with a charge voltage of 2.5, 3.0, 3.15, or 3.3 V. The charge current is programmable to 10, 50, 100, or 500 μA.

It is also stated in the document that the minimum RTC retention voltage is 2.05V. If the voltage drops below this level the RTC is likely to display wrong values, loose the configuration or return to the default settings once it reconnects. Make sure the RTC is properly powered at all times. How much power are you supplying through RTC_PWR?

Sergio

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Sergio_A_Intel
Employee
58 Views

Hi,

The circuit seems to be ok. According to the datasheet those are Zener diodes so the design is correct. That leaves the issue to be most likely power related. Have you seen section 4.13 of the Edison module Hardware guide http://www.intel.com/content/www/us/en/support/boards-and-kits/000005808.html Compute Module Hardware Guide for Boards and Kits? There you'll see:

The PMIC can be programmed with a charge voltage of 2.5, 3.0, 3.15, or 3.3 V. The charge current is programmable to 10, 50, 100, or 500 μA.

It is also stated in the document that the minimum RTC retention voltage is 2.05V. If the voltage drops below this level the RTC is likely to display wrong values, loose the configuration or return to the default settings once it reconnects. Make sure the RTC is properly powered at all times. How much power are you supplying through RTC_PWR?

Sergio

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