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TM4C1290NCPDT: Design of Hibernation Module battery backup.

Doug Broadwell
Expert 1175 points
Part Number: TM4C1290NCPDT

I need to add a backup battery for the Hibernation Module.  The obvious solution is one of the Lithium chemistries, but they all have fully charged voltages of 4 volts or higher, but the Hibernation Module has a maximum input voltage of 3.6 volts.  Suggestions?

Thanks.

  • 0
    TI__Guru*** 135355 points
    Hello Doug,

    I would say use something like the CR2032 which is a 3V lithium battery. That kind of battery fits with the voltage profile for VBAT (nominal voltage is 3V which is typical for VBAT, and end-point voltage is 2V where VBAT minimum is 1.8V). That is commonly used with TI reference designs for MCU's like MSP430 as well as some wireless EVM's.
  • 0 in reply to Ralph Jacobi
    Expert 1175 points
    Thanks Ralph, but I'm still concerned about the fact that all of the battery charging IC's I've looked at charge the battery to 4.0 or 4.1 or 4.2 volts, which exceeds the 3.6 volt max on the Vbatt line.
  • 0
    Expert 1175 points
    Is there a reference design schematic that I can look at?
  • 0 in reply to Doug Broadwell
    TI__Guru*** 135355 points
    Hello Doug,

    I am not an expert of battery charging IC's, but from what I learned about battery chemistry and topology, if you pick the right chemistry then you would not charge it beyond the usual maximum voltage of operation. What I don't know is if there are re-chargable coin cells like the CR2032 available at a cost effective level and if TI offers battery chargers for them.

    Alternatively you could use a buck converter to drop a higher voltage down, though if the battery is only for hibernate and nothing else that seems a bit excessive.

    Frankly, this particular E2E forum is geared towards support of TM4C from a peripheral and software standpoint, and I don't have any expertise in battery chargers and battery topologies. At a brief glance of the TI Battery Chargers portfolio, there may be options for 3.5V batteries or even Cell batteries which I am guessing means Coil Cell a la the CR2032? I do see your point about the 4+V mentions though.

    The good news however, is that we do have a whole forum of experts who specialize in this topic, so I would suggest that you make a query of them about such details. Here is a link to their forum: e2e.ti.com/.../179

    And regarding your question about reference designs, I checked our TM4C reference designs but none of them use batteries unfortunately, we usually don't see TM4C+batteries due to the applications the device usually ends up in. Applications with USB, Ethernet, CAN etc. typically don't leverage batteries which is why we really aren't equipped to talk to these points (I wouldn't be surprised if the MSP430 team who specializes in low power MCU's would have more knowledge as well as reference designs available).
  • 0 in reply to Ralph Jacobi
    Guru 117855 points

    If I may 'join this fray' - and if poster's intent (or new consideration), 'IS to include integral battery charger capability' - then the addition of a, '3V3, LDO Regulator' (which supplies all & only 'MCU related' - seems not so 'deal busting.'       (indeed adds (some) size/cost - yet  insures that 'when needed' - the  charger is ALWAYS available!)     NOT to ask - 'how many times' - this guy has misplaced or forgotten - the 'special' (external) charger!

    Another benefit of  such an, 'Integral - thus 'always there' charger' is the, 'Acceptance of wider ranged, product (and/or charger) voltage inputs.'     (common USB ports yield (very) S L O W charging rates - instead - accommodating broader voltages (& higher currents) enables far faster charging - from an abundance of sources!)      Such has saved my  butt  - MANY times.    (especially when 'remote ... thus desperate!')

    **************************************  

    Now of course - I (only now) - note the "Hibernation Module' - battery focus.    Adult beverages AND Sailing all day (may occasionally) blunt full focus...    

    There is GREAT & GROWING VALUE in providing a, "Cordless, Re-Chargable, Powered Product."    That said - the 'value proposition' - advanced in support of a 2500mAh Li-ion Battery - employed for 'Hibernation ONLY' - proves a 'hard sell.'     You may wish to consider adding 'Battery OR External Power' as the 'overall Power Source'  for  your product.    You may note that 'Cordless Power Tools' are rapidly replacing their 'line powered' (even) 'air-powered'  brethren!    And of course - 'CORDLESS proves so CONVENIENT' - when 'Working upon a boat @ sea...'

    One final note - we've not noted a, 're-chargable coin cell.'    (earlier mentioned CR2032/similar)    There ARE now Lithium Cells - in both AAA & AA format (not rechargable) - which (when in series) may yield 'MCU Acceptable' ~3V.    While LONG OUTLASTING (any) coin-cell...

    BE ABSOLUTELY SURE to CHECK/VERIFY - prior to such use!     (and note my 'Providers of Content' safeguard (page bottom) w/in forum boilerplate...)

  • 0 in reply to cb1_mobile
    Expert 1175 points

    Thanks for the thoughts, your idea of going with a long lived lithium primary cell may be the way to go.  The application is big and heavy and mains powered, the battery is just to use the Hib Module for a day/date clock.

  • 0 in reply to cb1_mobile
    Expert 1175 points
    Also, your idea of an LDO regulator with low quiescent current is good. Thanks also, Ralph, for the link to the battery charger forum, I've posted there and see what I get.
  • 0 in reply to Doug Broadwell
    TI__Guru*** 135355 points
    Hi Doug,

    Thanks for letting me know you posted, I added some internal comments to the team as well, hopefully they can help you better!
  • 0 in reply to Doug Broadwell
    Guru 117855 points

    Thank you - felt 'no pain' while responding - and only once 'deeply in' - did your "Hibernation Focus" catch my (impaired) notice!

    As you clarify:  'Application is big and heavy and mains powered'  the addition of a, '3V3, LDO Reg. - coupled to a Li-ion cell'  (ideally from one of the 'Big 4') - indeed makes great  (I believe 'chart-topping') sense. (especially when properly recharged)

    At the 'risk of blasphemy' - do note that 'Lithium targeted, Recharge ICs' exist' - which include such integral ~3V3 regulator.      (you may have to visit (pardon) 'alien shores' - should this vendor (not) offer such (valuable) 'extra bit.'      Also - most such 'recharge ICs' appear to  'target multiple Lithium batteries - connected in series' - each one individually monitored & excited.    (far exceeding (your) needs - and resulting in charger ICs being (both) physically larger and more costly!)    

    Alternatively - your 'one & only one' - battery recharge requirement - may be best answered via, 'spare pins on your MCU'  (to include ADC - to monitor battery voltage & current.) along w/several added, strategic components.      (earlier 'blasphemy' may have (just now) been negated...)

    Your study of top performing, specialty charger ICs (across several, recharge IC 'leaders') - should provide an excellent framework for you to (selectively) 'model.'       (and your single Lithium Cell - greatly 'speeds/eases' - such design...)