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BQ25504

Don Pitchford
Intellectual 255 points
Other Parts Discussed in Thread: BQ25504, TPS63001

I am racking my head around energy harvesting.    I have a circuit that needs to be charge either from USB or from solar panel and needs to provide a constant 3.3voltage output.   I am trying to do it with minimum chips and was hoping I could get away with the BQ25504.   

However,  What I am seeing is that I still need a 3 chip design unless I am missing something. 

I need:

  • USB Charging -  MAX1555.
  • Solar Charing - BQ25504
  • Constant 3.3v output - TPS63001.

Is this proper direction, or is there another solution that I can meet my needs with a single chip design?

Don

  • 0
    TI__Mastermind 31120 points

    There are no design requirements (Pin, Pout), no charge element, so I can't say what will work.

  • 0 in reply to Charles Mauney
    Intellectual 255 points

    I agree with your statement.  I should of posted a circuit diagram.   Here it is...  

    I have solar panel that feeds into the BQ, which should charge the Li-Ion battery pack up to 4.1v.    However, only see it going to 3.6v.    The VSTOR is fed into the TPS63001 to to generate 3.3v.      The MAX 1555 is used to charge the battery if the USB is plugged in.  

    Is this the right direction?    Can I eliminate the MAX1555 and have the USB tied directly into the BQ Vdc_in?  

    Don

    temp.pdf
  • 0 in reply to Don Pitchford
    TI__Mastermind 31120 points

    You need some sort of step down conversion device between the USB input and the battery.

    Since there are still no requirements it is hard to give you valid solutions.

    What is the valid range of the 3.3V supply?  If you put 4.1V into it, won't it go above 3.3V.

    If the 3.3V is allowed to go down to 3.15V, then most of the energy is out of the Li-Ion cell and you really don't need a second boost converter....maybe a buck with 100% duty cycle, which is probably more efficient than a boost converter.

  • 0 in reply to Charles Mauney
    Mastermind 7850 points

    Hi,

     I have a similar problem to solve - being able to use a multiple power inputs (energy harvested and from USB) to charge the battery,

    preferably with automatic switching without the need of changing jumpers

    I see from the specs for bq25504, Vin = 0.13 - 3V that as you said an extra converter is needed to bring the voltage from USB down to 3V (or less)

    to satisfy the bq25504 Vin requirements.

    I need an output of +3.0V/100mA to supply my system (WSN node), so will use an LDO connected to Lithium Polymer battery.

    Can bq25504 charge the battery, while the system load is connected?

    What are the setup resistors values for a 600mAh lithium polymer battery and solar panel input?

    Jan