• State TI Thinks Resolved
  • Locked Locked
  • Replies 7 replies
  • Answers 3 answers
  • Subscribers 63 subscribers
  • Views 709 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

BQ25570: Power management forum

Nikos Antoniou
Intellectual 820 points
Part Number: BQ25570
Other Parts Discussed in Thread: BQ51050B, , BQ25505, TLV751, TPS7A05, TPS7A03, TPS7A02

Dear Sir / Madam

We are currently designing an IoT device that should provide wireless charging capabilities as well as an energy harvesting mechanism.

So far, the dominant ICs are the bq51050B for the wireless charging and the bq25570 for energy harvesting

Looking at the datasheet of the bq25570 I couldn't identify whether or not it is suitable for Li-Ion / LiPo batteries. Is the bq25570 IC capable of properly and safely charging Li-Ion / LiPo batteries?

For energy harvesting, we are going to use piezoelectric sensors

This is how I am intending to combine both ICs, do I need to take anything else into consideration? Could the circuit operate normally with the configuration below?

Thanks in advance

  • 0
    TI__Genius 12485 points

    Hi Nikos,

    Yes this BQ25570 IC is capable of charging Li batteries. I would connect the battery pins (VBAT pin on BQ25570 and the BAT pin of BQ51050B) together as the DC-DC converter output voltage will be very limited. 

    As far as the piezo is concerned- are you able to get enough power from the piezo at the frequency you are operating? Also do you intend to shutoff energy harvesting when the wireless charging coil is present?

    Let us know if you have any questions.

    Regards,

    Gautham

  • 0 in reply to Gautham
    Intellectual 820 points

    Thank you for your prompt response. I've reconsidered the design by replacing the existing boost charger with the bq25505 and adding a dual LDO.

    The harvester will act as an auxiliary charging system while the wireless charging will be the main. The system will be mounted inside an insole and I believe that I could harvest some energy from footsteps.

    The main idea is to combine both the wireless charging and energy harvesting to charge to Li-Ion battery and then use an LDO to supply the system. This is how I am thinking to combine the bq25505 , bq51050 and tps71202

    Moreover, yes I am intended to shutoff energy harvesting while the wireless charging, so I believe that I have to drive the EN pin high during this mode, isn't it? Is there any problem in case that I do not shut down the harvester?

    In general, the architecture is it correct? Do I need to take anything else into consideration, such as battery management ic for example?

  • 0 in reply to Nikos Antoniou
    TI__Genius 12485 points

    Hi Nikos,

    Yes the sketch you have seems to work. On the LDO- are you okay with the current consumption?  Are you prioritizing the combo over having two LDOs feeding from the same pin? We have newer LDOs which could be much more lower Iq than the one you have- http://www.ti.com/product/TPS7A05

    You might also look into possibly a buck for higher efficiency since your application seems to be a low power system. 

    You are correct- Driving EN pin high when the wireless charger present is okay. Also given your application, it helps us automatically as the piezo won't be delivering power when its sitting on a TX :)

    Let us know if you have any questions. 

    Regards,

    Gautham

  • 0 in reply to Gautham
    Intellectual 820 points

    Dear Gautham,

    Thank you for your prompt reply.

     Are you prioritizing the combo over having two LDOs feeding from the same pin? Could you be more specific please?

    You might also look into possibly a buck for higher efficiency since your application seems to be a low power system. Yes, but I will sacrifice the advantage of the low dropout voltage isn't it? I need a 3.3V rail and Li-Ion batteries are fully charged on 4.2 - 4.1V

    On the LDO- are you okay with the current consumption? Do you have any suggestions for 250mA dual output with low Iq?

    Thanks in advance

    Nick

     

  • 0 in reply to Nikos Antoniou
    TI__Genius 12485 points

    Hi Nikos,

    On the prioritization- I was wondering why you wouldn't just have two separate LDOs connected from the same pin for input instead of using one with dual output as there might be lower Iq LDOs in our portfolio which might be great for energy harvesting applications. 

    I will forward your note to the LDO team here who might be able to comment on any dual output LDOs. 

    Regards,

    Gautham

  • 0 in reply to Gautham
    Intellectual 820 points

    Thank you Gautham,

    In the meantime, I will examine the scenario of adding two LDOs with lower Iq.

    Nick

  • 0 in reply to Nikos Antoniou
    TI__Expert 4320 points

    Hi Nick,

    Currently our lowest Iq dual-channel device is our newly released TLV751.

    For low Iq, we have recently released the next-gen of TPS7A05, the TPS7A02 and TPS7A03 boasting 25nA / 200nA Iq.

    Could you use two TPS7A02? It is in a fairly small 1x1mm package or SOT-23.

    regards,

    Wilson