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AM3352 RTC

Nikhil Tiwari
Intellectual 575 points

Other Parts Discussed in Thread: AM3352, TPS65910

Hi,

I have few queries regarding the RTC feature of AM3352 -

  1. In AM3352 datasheet it is given that the RTC maximum current for CAP_VDD_RTC and VDDS_RTC is 2mA and 5mA respectively. What are the typical current requirements for RTC? General purpose EVM wiki page http://processors.wiki.ti.com/index.php/AM335x_General_Purpose_EVM_HW_User_Guide mentions the VDDS_RTC power rail as 10mA.
  2. We want to use processor RTC with lowest possible current when all other power supplies for AM3352 are down. As per the TRM we can use RTC only mode along with RTC LDO switched OFF (the RTC power will be supplied using a super capacitor). In this case what will be the standby current requirement to keep the RTC functioning?
  3. We are also considering to use TPS65910A3A1's RTC as rated current output for RTC LDO of TPS65910 is given as 0.1mA in back-up mode. As we are using a super capacitor to provide back-up supply for RTC what will you suggest as a the least power solution (AM3352, TPS65910 or any external RTC IC). 

Thanks & Regards,

Nikhil 

  • 0
    TI__Guru**** 393215 points

    Hi Nikhil,

    Nikhil Tiwari said:
    In AM3352 datasheet it is given that the RTC maximum current for CAP_VDD_RTC and VDDS_RTC is 2mA and 5mA respectively. What are the typical current requirements for RTC? General purpose EVM wiki page http://processors.wiki.ti.com/index.php/AM335x_General_Purpose_EVM_HW_User_Guide mentions the VDDS_RTC power rail as 10mA.

    See this link: http://processors.wiki.ti.com/index.php/AM335x_Power_Consumption_Summary

    Nikhil Tiwari said:
    We want to use processor RTC with lowest possible current when all other power supplies for AM3352 are down. As per the TRM we can use RTC only mode along with RTC LDO switched OFF (the RTC power will be supplied using a super capacitor). In this case what will be the standby current requirement to keep the RTC functioning?

    You cannot supply the RTC directly from a supercap. The power supply must come from a stable 1.8V source. See Table 3-12 in the AM335X Datasheet Rev. F.

    We are also considering to use TPS65910A3A1's RTC as rated current output for RTC LDO of TPS65910 is given as 0.1mA in back-up mode. As we are using a super capacitor to provide back-up supply for RTC what will you suggest as a the least power solution (AM3352, TPS65910 or any external RTC IC). 

    The lowest power consumption should be reached with a dedicated external RTC. There are chips on the market that consume less than 0.5uA.

  • 0 in reply to Biser Gatchev-XID
    Intellectual 575 points

    Hi Biser,

    Thanks for the information. Based on this we will go ahead with the external RTC chip solution.

    Regards,

    Nikhil