AM4372: TPS65218D0 connection

Hi Sitara support Team,

Can someone please help me with this?
Or should I post this in the Power management forum?

If you can respond in this forum, I would appreciate it if you could let me know
when you plan to respond as I need to report this to my customer.

Best regards,
Kanae

I need some time to review your questions. I will try to reply by mid next week.

Regards,
Paul

Hi Paul,

Thanks for your reply.

I will share this information with my customers.
It would also be helpful if you could let us know
if there is any change in your reply schedule.

Best regards,
Kanae

Hi Paul,

Thank you for your support.

Please let me confirm about your reply,
"connect VDDS_RTC to any AM437x 1.8V supply and connect CAP_VDD_RTC to the same power source as VDD_CORE."

I know that the 1.8V used in AM437x is the power supply generated by LDO1 of TPS65218D0.
In TPS65218D0 Datasheet: Applications Without Backup Battery, Figure 6-1 CC Input to Power Path,
I think the power supply by DCDC5 and DCDC6 will be unnecessary,
but am I right in thinking that the power circuit by DCDC5 and DCDC6 is still necessary for the power sequence?

Also, are there any points to keep in mind when disabling the RTC function?

Best regards,
Kanae

Hi Paul,

Thank you for your support.

Is it better to post the additional questions on the Power Management forum
to get a faster answer?
I am looking forward to your advice to avoid a double thread.

Best regards,
Kanae

Sorry for the delayed reply. I got caught up working on another task and didn't see your last questions.

You will need to ask someone from the power management team to address your questions related to unused PMIC functions.

I was under the impression you were planning to use the real-time clock function of the RTC, but were not planning to use it while the other SOC functions were powered off (RTC-only mode), where it could be configured to wake-up the processor periodically.  So I'm not sure what you are asking with your question related to disabling the RTC function.

I will warn you that I'm not familiar with the various software configurations supported by our software support packages. I may be able to answer very specific questions about how the RTC works or the function of a register, but will not be able to help with software configuration questions. If you need this type of help, please tell me which software package you are using and I will try to find the correct person and assign this thread to them.

Regards,
Paul 

Hi Paul,

Thank you for your reply.

Paul: 
<I was under the impression you were planning to use the real-time clock function of the RTC, but were not planning to use it while the other SOC functions were powered off (RTC-only mode), where it could be configured to wake-up the processor periodically.  So I'm not sure what you are asking with your question related to disabling the RTC function.>

I would like to respond to your comment above.

I was aware that the RTC cannot be disabled because it uses TPS65218D0,
so I selected "RTC Timer Functionality but no RTC-only mode" on the assumption
that it cannot be disabled, which led to the above question.

If it is possible to disable the RTC even using the TPS65218D0,
please let me know how to connect it.

The customer's requirements are as follows

-TPS65218D0 is used
-RTC is not required
-S/W: iTRON

I appreciate  to your help in finding the right person and assigning this thread.

Best regards,
Kanae

The TRM clearly defines AM437x connection expectations when the RTC is not used.  See the comment below which was copied from the TRM.

If your application never uses the RTC functionality, connect RTC_KALDO_ENn to VDDS_RTC, CAP_VDD_RTC to VDD_CORE, and RTC_PWRONRSTn to ground. These connections disable the internal RTC LDO because RTC_KALDO_ENn is high, and they use the external VDD_CORE supply to power the RTC digital core. The RTC LDO must be disabled for internal power sequencing even though the RTC is not used. Grounding the reset signal will ensure the RTC stays in reset. Disabling the internal LDO will allow the application to achieve lower power consumption in all the low power modes.

Does this answer your question with respect to AM4372 connectivity requirements?

I'm not sure what "iTRON" means. I was expecting you to say Linux or RTOS. As mentioned before, I 'm not familiar with the various software offerings. Is this a software package support by TI?  If not, I'm not sure where you get support.

Regards,
Paul

Hi Paul,

Thank you for your quick reply.
I understood that the information in TRM is consistent with the RTC disable mode in Checklist.

Please let me go back to my post at the beginning of this thread and ask the question again.

Kanae:
<1. I understand that the RTC power supply is needed to make the power supply sequence
compatible with the PMIC (TPS65218D0). >

Q1: Am I correct in understanding that the above is not correct,
and that the TRM information for not using the RTC is "when using the TPS65218D0",
and that the RTC disable mode in the Checklist can also be selected?

Q2: The customer's system that he is considering now does not need the RTC function,
　but in order to make the power supply sequence compatible with the PMIC (TPS65218D0).
　So, he assumed that the RTC disable mode cannot be selected.
　In that case, he was considering changing the connection of the following pins
　by referring to "RTC Timer Functionality but no RTC-only Mode"
Is it necessary to change this?

-VDDS_RTC: Change the power supply from LDO1 to DCDC6.
-RTC_PWRONRSTn: Connect to PGOOD_BU (TPS65218D0).
-Pull up nWAKEUP to DCDC6 with 100kΩ.

"Current schematic around the PMIC"

Q3. If the change in Q2 is not necessary and there is no problem to select RTC Disable mode using TPS65218D0,
　should the customer's schematic be modified as follows?

-RTC_KALDO_Enn: Any AM437x 1.8 V power supply -> VDDS_RTC
-PMIC_POWER_EN : RTC_PMIC_EN → NC

Q4. do I need an inductor or some other circuit for the output?
　Or can I use a 10kΩ pulldown as I do now?

There may be some parts that are difficult to understand due to my poor English,
please feel free to point out any unclear points.

For S/W, it seems to use iTRON provided by a third party based on information from TI_RTOS.
I am aware that you cannot provide support for this.
Please let me check only the H/W connection method this time.

Best regards,
Kanae

Hi Paul,

Thank you for your reply.

For Q1, I had referred to the following post and determined that
RTC disable mode cannot be selected when using PMIC.

e2e.ti.com/.../890446

I understand that RTC disable mode can be selected from the AM4372 side.

I will post Q2, Q3, and Q4 in the Power Management Forum.

If the customer is using the combination of TPS65218D0 and AM437x and
the following user's guide connection is required,
I will inform the customer to select the RTC only mode.

www.ti.com/.../slvuaa9b.pdf

Best regards,
Kanae

I sent Ahmad an email asking what he meant in his reply to the E2E post you referenced. I will let you know as soon as I hear from him.

Hi Paul.

Thank you for your reply.

I will check with the customer if it is possible to accept the configuration
in the user guide (RTC only mode in the checklist).

I appreciate your kind support.

Best regards,
Kanae