BBB based design w/TPS65217C - Any issues switching between AC and USB inputs if no Battery used?

PSB

unread,

Nov 23, 2015, 2:26:30 PM11/23/15

to BeagleBoard

Hi,

We are designing with the AM3352 and TPS65217C PMIC closely matching the BBB. We have two power inputs (Primary and backup) coming from different PS. We intend on connecting the primary to the AC input of the TPS65217 and connect the backup to the USB input. We do not have a battery in our system and need to the TPS to auto switch between the AC/USB sources when the AC input is lost.

TPS datasheet section 9.3.9.1 says that it is not recommended using this mode if the battery is absent. I checked with TI who said that this mode, while not recommended, has been widely used and is also on the BBB. TI suggested posting my question on the BBB forum to see if anyone has had any issues or Lockout conditions when using the BBB or their custom design in this mode. I will appreciate if anyone can share their experience in applications similar to mine?

Thanks in advance.

Gerald Coley

unread,

Nov 23, 2015, 2:27:36 PM11/23/15

to beagl...@googlegroups.com

I have seen no issues.

Gerald

--
For more options, visit http://beagleboard.org/discuss
---
You received this message because you are subscribed to the Google Groups "BeagleBoard" group.
To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

--

Gerald

ger...@beagleboard.org

http://beagleboard.org/

John Syne

unread,

Nov 23, 2015, 3:17:10 PM11/23/15

to beagl...@googlegroups.com

Why not use something like this before the TPS65217C:

http://www.linear.com/product/LTC4415

Regards,

John

PSB

unread,

Nov 23, 2015, 4:01:45 PM11/23/15

to BeagleBoard

Thanks John... Appreciate your response. I am considering a similar TI part to the LTC as an alternative solution.Meanwhile, I just wanted to see if anyone had experienced any issue using the PMIC in that mode.

Maxim Podbereznyy

unread,

Nov 24, 2015, 4:32:32 AM11/24/15

to beagleboard

you will definitely have random reboots like regular BBBs have it. There are hundreds of posts here and I am not sure that the issue was solved in the current kernel. You can't enable 3 power sources at TPS65217 simultaneously, only two of them. You can switch off Vac input, but Vbat is always enabled. I suppose random reboots will not take place if you physically disconnect Vac and USB0_VBUS.

--

LinkedIn - http://www.linkedin.com/in/maximpodbereznyy

Company - http://www.linkedin.com/company/mentorel

Facebook - https://www.facebook.com/mentorel.company

John Syne

unread,

Nov 25, 2015, 2:12:21 PM11/25/15

to beagl...@googlegroups.com

My thinking is that TI added that clause to the datasheet for a reason. There is probably some corner case that causes the switch to fail and hence why TI added that clause. My advice is to stay away from using the TPS65217C in this way and rather add circuitry on the front end that works every time. BTW, I’m not familiar with a TI device that performs this functions. Do you have a part number you can share?