Unexpected current consumption with PMIC Sleep mode (for battery charging)

[Dan Julio]

I would like to have battery charging enabled when the rest of the system is powered down.

I have a test system based on the pocketbeagle running the current debian beaglebone release (4.14.71-ti-r80).

Normally the kernel sets the PMIC STATUS.OFF bit so that when it powers down the PMIC enters OFF state. This powers off LDO2 as well as disables charging. However with STATUS.OFF clear then the charger is enabled to run (as well as LDO2 enabled to power the RTC). My understanding of the TI errata for the processor is that earlier problems with additional quiescent current are gone in post-revision 1.0 silicon (Advisory 1.0.17 in the TI errata for the processor).

However when I attempt to enable charging after power-down I see a quiescent current of ~15 mA from the battery (after it is finished charging). The pocketbeagle has a SN74lvc1g07 driver also taking power from the LDO2 output but its current should be far less than 1 mA.

It seems that some circuitry in the Octavo module is taking additional power. Can you explain this and is there a way to disable the extra power consumption so we can implement systems that can charge when the system has been shut down?

In addition, I see that the TL5209 output is also enabled in this case. Can you explain how it is enabled?

Thanks, Dan

[Erik Welsh]

The additional current consumption comes from the fact that the OSD335x and OSD335x-SM use TPS65217C PMIC.  If you look in the application note from TI (http://www.ti.com/lit/ug/slvu551i/slvu551i.pdf), you can see that in the case of the TPS65217C, both VDDS and VDDS_RTC are connected to the LDO1 output of the PMIC.  The additional current consumption that you see is a result of the VDDS power input being connected to the LDO1.

Unfortunately, the connection between VDDS and LDO1 is internal within the SiP and cannot be modified on the OSD335x and OSD335x-SM.  However, we are in the process of characterizing the OSD335x C-SiP to see if it can support the power use case where VDDS is not connected to LDO1.  We should have that characterization finalized in early January.

Additionally, the TL5209 is enabled with an internal pull up within the OSD335x family of devices.  In the OSD335x and OSD335x-SM, this connection cannot be modified.  However, in the OSD335x C-SiP, there is a pin, SYS_VDD1_CTL, that will allow a user to disable the TL5209.

 

[Dan Julio]

Ok. Thank you for explaining and for correcting that it’s actually LDO1.

[Dan Julio]

Hi Erik,

Have you completed the characterization of the OSD335x C-SiP to see if it can support the lower power use case where VDDS is not connected to LDO1?

Thanks, Dan

[Erik Welsh]

Dan,

We have done some preliminary characterization of the OSD335x C-SiP’s support for RTC-only mode and the results are encouraging.  Unfortunately, it will take us a little while longer to finish up the work needed to publish the application note on using RTC-only mode with the C-SiP.  In the meantime, I would encourage you to fill out the contact form (https://octavosystems.com/contact/) so that we can directly discuss the preliminary characterization results and what would need to be done connection-wise to enable the RTC-only support since I do not want to discuss preliminary findings on the forum.  If not, I will make sure to update this thread with a link to the application note once it is published.

Thanks,

Erik

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