Power off issues

[JarekD]

Hi all,

I have doubts if powering off the device based on OSD-3358-512M-ISM at some random moment (just removing the power supply) may cause any issues with system files. What if the power supply removal occurs while the system is writing some file to eMMC? I assume that the system will be booted from eMMC and SD Card will be for data storage.

I know that I can use a backup battery but I don’t have space for it. Can I use some kind of backup circuitry based on capacitor connected to VBAT? How big capacitance do I need? Is it possible to configure the SiP in the way that it will decrease the power requirements after main power (connected to AC or USB) is removed, and then it will finish its tasks and shut down using the remaining power in the capacitor connected to VBAT?

Is it any other hardware or software solution to protect the data on eMMC or SD from corruption caused by sudden power supply removal?

Or maybe the SiP is designed in the way that I do not need to worry about these issues?

Thank you in advance

[Eshtaartha Basu]

Hello JarekD,

eMMC memories are less susceptible to data corruption compared to SD card due to their integrated memory controllers (load balancer). However, you may lose temporary files stored on DDR3 because of a power loss.

Please refer the following forum thread for information on using VIN_BAT for backup:

automated power up/power down sequencing

The size of the super capacitor required depends on the power consumption figures for your specific design. We have not tested any super capacitor with OSD335x. Hence, we do not recommend any particular super capacitor. We do not provide any additional hardware/software solution to prevent data corruption. As discussed in the above thread, to prevent data corruption, choose a temporary power source (super cap in your case) that could power your board long enough for it to shutdown properly after PMIC_PB_IN is asserted (due to main power loss) by an external logic.

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