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SR11
New Contributor I
1,903 Views

RTC battery voltage range and connections

Hi,

Please reply to following queries regarding RTC:

1. What is the voltage range of battery that can be connected to V_VBAT_BKUP pin (pin23 on the edison, pin 5 of J18 on the mini breakout)?

2. Can the -ve terminal of battery be connected to any common ground?

3. What is the power rating of the RTC circuit?

4. Can we connect rechargeable battery to RTC? What are the configuration settings to enable the recharge when power is on?

5. On Mini breakout board, can I connect the same 3.7V battery to J2 & V_VBAT_BKUP?

Regards

Srikanth

5 Replies
Sergio_A_Intel
Employee
260 Views

Hi,

  1. The minimum RTC retention voltage is 2.05. The normal operation values are 2.5, 3.0, 3.15, or 3.3 V.
  2. You can connect the RTC to any of the GND pins of the Edison. These pins are 1,5,9,11,13,15.
  3. What do you mean specifically with the power rating? You can see information of the electrical characteristics in section 4.13 of http://www.intel.com/content/www/us/en/support/boards-and-kits/000005808.html Compute Module Hardware Guide for Boards and Kits
  4. Yes, you can connect either a rechargeable coin cell batteries or super-capacitors. When the device you're using runs low on power you need to power your board directly so the RTC can continue to work. While powering your board you can disconnect the battery to recharge it and then connect it again when the battery is fully powered.
  5. Yes, you can connect a 3.7V battery to J2. Other users in the community have connected a 3.7V battery to J2 successfully.

Let me know if this was helpful.

Sergio

SR11
New Contributor I
260 Views

Dear Sergio,

Thanks your for replying to the queries!

3. Section 4.13 is discussing the charging configuration settings for backup battery. I would like to know the typical power consumed by the RTC oscillator circuit.

4. Won't the battery connected to J2 be automatically charged while main power is On?

5. Will battery connected to J2 power up the RTC oscillator also?

Regards

Srikanth

Sergio_A_Intel
Employee
260 Views

According to http://download.intel.com/support/edison/sb/edisonbreakout_hg_331190006.pdf http://download.intel.com/support/edison/sb/edisonbreakout_hg_331190006.pdf

"When you attach a rechargeable lithium-ion battery, the breakout board will recharge the battery whenever power is applied via J21 or J22, or via J3 (when the board is attached to a USB host)."

This means that both 4 and 5 are yes. As for question 3, it seems this information is not available on the document. I'll investigate further and contact you back soon.

Sergio

Sergio_A_Intel
Employee
260 Views

We performed some tests on the power consumed by the RTC circuit. We tested the Edison breakout board with a standard lithium battery cr2032 attached to the RTC backup battery input (J18-pin5) and ground (J19-pin 3). When Edison is powered on (using a 12V power supply) the RTC power consumption is 1.2μA * 3.3V ~= 4μW, when Edison is off and has no power supply attached (just the battery) the RTC power consumption is 8.2μA * 3.3V ~= 27μW.

Sergio

SR11
New Contributor I
260 Views

Hi Sergio,

Thank you very much

-Srikanth

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