• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Subscribers 102 subscribers
  • Views 1252 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Question about AM437x RTC

g.f.
Guru 15510 points
Other Parts Discussed in Thread: TPS65218

Hi,

I have questions about AM437x RTC.

The question is about power supply for CAP_VDD_RTC / VDDS_RTC and
power consumption of RTC.

Q1.If using RTC functionality and RTC-only mode,
   CAP_VDD_RTC doesn't need power supply but need to connect to VSS via decpoupling capacitor(1uF),
   and provide 1.8V power supply to VDDS_RTC, is it correct?
   
Q2.If using RTC as RTC-only mode, do I need to provide power supply as following?
   - CAP_VDD_RTC = 1.0V
   - VDDS_RTC = 1.8V

Q3.When supplying from backup battery, what is the consumption current value required
   for time measurement and time maintenance?

Q4.What is the consumption current value of RTC when the main power is ON?

I found power estimation tool, but power consumption of RTC can't be judged from the tool.
But I want to know the RTC power consumption, is there any information for Q3 and Q4?

best regards,
g.f.

  • 0
    TI__Guru**** 393215 points

    Hi g.f,

    For Q1 and Q2 please see this wiki: http://processors.wiki.ti.com/index.php/AM437x_Schematic_Checklist#RTC

    Q3 VDDS_RTC must be provided from a regulated 1.8V power supply, it cannot be connected directly to a backup battery.

    Q4 http://processors.wiki.ti.com/index.php/AM437x_Power_Consumption_Summary has some data, but is far from complete yet. Device characterization is still ongoing.

  • 0 in reply to Biser Gatchev-XID
    Guru 15510 points

    Hi Biser,

    Thank you for the reply.

    *About Q1&Q2:
    I checked the TI wiki page which you send to me.
    I'm little confused at RTC-only mode written in the Table.
    In the Table, CAP_VDD_RTC required 1uF decoupling capacitor to VSS
    but in the TRM(spruhl7a) page.255 "Figure 6-5. High Level System View for RTC-only mode,
    CAP_VDD_RTC are provided 1.0v power supply from PMIC.
    Which is correct ?

    *About Q3:
    Yes, I understood that backup battery can't be connect directly.
    I'm sorry, my explanation wasn't good.
    What I want to know is "consumption current value required for time measurement
    and time maintenance" when PMIC are supply from backup battery as
    Figure 6-5 of TRM page.255 .

    *About Q4:
    Is there a plan to share the consumption current value of RTC in the near future?
    For example, AM335x RTC power consumption wasn't provided.
    It was mixed with "all 1.8V power consumption".
    I need to tell to my customer, so please tell me the plan if you know.

    best regards,
    g.f.

  • 0 in reply to g.f.
    TI__Guru**** 393215 points

    g.f. said:
    *About Q1&Q2:
    I checked the TI wiki page which you send to me. I'm little confused at RTC-only mode written in the Table. In the Table, CAP_VDD_RTC required 1uF decoupling capacitor to VSS but in the TRM(spruhl7a) page.255 "Figure 6-5. High Level System View for RTC-only mode, CAP_VDD_RTC are provided 1.0v power supply from PMIC. Which is correct ?

    CAP_VDD_RTC is the output from the internal RTC LDO. This LDO is enabled when RTC_KALDO_ENn is pulled low. In this case a 1uF capacitor must be attached to CAP_VDD_RTC. When RTC_KALDO_ENn is pulled high the internal RTC LDO is disabled and 1.1V must be provided to pin CAP_VDD_RTC from the PMIC.

    About Q3 and Q4, the AM437X characterization is ongoing and data will be provided when it becomes available.

  • 0 in reply to Biser Gatchev-XID
    Guru 15510 points

    Hi Biser,

    Thank you so much for the support.
    I understood.

    best regards,
    g.f.

  • 0 in reply to Biser Gatchev-XID
    Prodigy 40 points

    Hi Biser.

    We are using RTC-only mode and face fast battery discharge. We are using PMIC to generate 1v8 and 1v0 and switching internal LDO off (KALDO_ENn  PU to 1V8) . 

    I wonder why the 1v8 out from PMIC is not used in " AM437x General Purpose EVM  " instead external LDO is used to provide 1v8 for the VDDS_RTC, also the KALDO_ENn is PD thru 10K, (that mean internal LDO is ON), but CAP_VDD_RTC is tied to 1V0 output of PMIC (TPS65218).

  • 0 in reply to Vladimir Melnikov
    Prodigy 40 points

    Now i know.

    Pmic switches off DC/DC for RTC once the battary is removed or unplugged. so they provided external power supply for RTC to avoid that issue.

    What we do - we switch dedicated bit in 65218 to enable DC/DC. that was not done in TI driver.