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TM4C129XNCZAD: Power consumption on VBAT pin when VDD is ON

Shrikrishna K
Prodigy 100 points
Part Number: TM4C129XNCZAD

Hi,

I am trying to calculate RTC battery life.

It is given in datasheet that current consumption in hibernation module is max 2.14uA.

Also given that, current consumption from VBAT (IHIB_VDD3ON) and when in hibernation mode is max 46.2uA. 

What would be current consumption from VBAT when in normal operation (VDD and VDDA is ON, 3.3V).

Thank you

Krishna

  • 0
    TI__Guru**** 191486 points
    Hi Krishna,
    Do you mean to ask for the VBAT current during normal operation as if all the modules are active and SYSCLK is running at full frequency (i.e. 120MHz)? We do not have this parameter characterized perhaps it is not a normal use case. In VDD3ON mode the internal VDDC (1.2V) is powered off but VDD (3.3V) continues to supply power to the Hibernation module. Since the VDDC is turned off most of the internal logic has no power so I will expect the Vbat current to not be much higher than Vbat current in hibernation mode. However, I can't quantify this. You can try to do some measurement and let us know what you find.
  • 0 in reply to Charles Tsai
    Guru 117855 points

    Beyond the able reply of vendor's Charles - most such MCU implementations (those properly designed) draw (little) beyond "battery's leakage current" (usually <5uA, sometimes far less) when the "normal" power supply is in operation...

    Should it not prove, "Quick/Easy" for you to insert a proper meter in series w/your candidate, "RTC Battery" and execute such measurement?     You are interested in the behavior of "your" battery - thus this (more personal/focused/targeted) approach proves superior...     And - as an additional benefit - best enables your "compare/contrast" of multiple candidate batteries - under their (exact) usage conditions - that's substantial - is it not?

  • 0 in reply to cb1_mobile
    Guru 27665 points
    Additional question (Really it's not a Socratic one), is it not fairly common for the battery and power supply to be diode or'ed? Or is the VBAT input supposed to remove that necessity?

    Robert
  • 0 in reply to Robert Adsett
    Guru 117855 points

    What ..."too complicated" - does not the "MCU vendor's (LIKE-less) drum BEAT - ALWAYS & ONLY - to "More, more, more" (too often) even "over-flowing" the targeted, "Kitchen Sink!"

    Are we to "forget" stilted/stalled performance - be "Ooh'ed-Aah'ed" instead - by (imperfect add-ons)?

    Manhattan (top valued NYC real-estate - for others) was "sold" to the natives for "trinkets" - is that "strategy" (still) being deployed?