关于imx287 RTC 的问题

[136988129]

有一个关于IMX287板子的问题，A15引脚，我只是使用RTC功能，当板子断电的时候 纽扣电池给A15引脚供电，以保证RTC 计数器 继续工作

但是我看datasheet的时候，上面建议的电压是3.1V~4.2V  可是我的纽扣电池电压在1.5V~3V，

还有datasheet上也有说到A15引脚的电压范围是-0.3V~4.2V

所以我想请问一下  我不使用电池给整个板子供电 只是 在power-down的情况下 RTC正常工作    A15引脚的电压给多少合适 

[weidong_sun]

Hello Haijun,

    Battery and DCDC_BATT pins are for 4.2V LI battery connection, not for Li-Coin cell batter.  If you don't use Li Battery for your project, you can use single 5V power. more detailed information, please refer to AN4199.pdf. here is the link:

i.MX28 Evaluation Kit | NXP 

If you need Real time clock, external RTC chip is recommended.  NXP also has many types of RTC chip, see the link, please!

Real-Time Clocks | Ultra-Low-Power RTC | NXP 

The Li coin cell battery can be used for these RTC chip.

Have a nice day!

BR,

Weidong

[136988129]

I saw another answer like this, instead of using an external rtc chip, I want to make sure that the answer is correct？

iMX287 RTC 

[weidong_sun]

Hi Haijun,

    我不知道你是否明白我的意思，如果你用I.MX28做手持设备，那么就需要使用类似有机电池一样的满电4.2V的锂电池。那么这个时候，配置I.MX28寄存器是有效的：即在关机模式下，保持RTC运行。

    但是，你的项目不使用这种锂电池，仅仅是需要RTC保持住时钟，那么你不能再DCDC_BATT和BATT脚接纽扣电池，这会一起动，瞬间纽扣电池就没电了。

     建议你用独立RTC，还有一个很重要的原因，就是I.MX28内置RTC功耗比较高，外部独立RTC功耗很低，一个纽扣电池可以用很久，甚至2-3年都可以。

     如果你的项目要求是移动设备，使用4.2V锂电，那么你用内部RTC，没有任何问题。

Reply in English:

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I don't know if you understand what I mean. If you use the i.mx28 as a handheld device, you need to use a fully charged 4.2V lithium battery like an organic battery. At this time, the configuration of i.mx28 register is effective: that is, keep RTC running in shutdown mode.
However, your project does not use this kind of lithium battery, just needs RTC to keep the clock, so you can no longer DCDC batt and batt pin button batteries, which will move together, and the button battery will be dead in an instant.

It is recommended that you use independent RTC. Another important reason is that i.mx28 has high internal RTC power consumption and low external independent RTC power consumption. A button battery can be used for a long time, even for 2-3 years.

If your project requires a mobile device with a 4.2V lithium battery, you can use the internal RTC without any problems.

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Have a nice day!

BR,

weidong

[136988129]

Thank you very much, I understand.