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Looking for a reference design for a Rechargeable 5VDC design

Bob Shankle
Expert 1180 points
Other Parts Discussed in Thread: BQ24040

Hi Folks,

I'm working on a mobile device that needs a rechargeable battery pack.  Most of the components run on 3.3vdc, but I have a cellular modem that wants 5VDC supplied.

Can someone point me to some reference designs so I can look at the various options available?

thanks,

Bob

  • 0
    TI__Guru**** 166006 points
    Bob,

    Can I get a bit more information from you like, the battery chemistry, number of cells in series/parallel and capacity, input power source for charging the battery, operation while charging?
  • 0 in reply to Jeff F
    Expert 1180 points

    Hi Jeff,

    Thanks for the reply.  I am open to various battery chemistry and #cells.  The charging method would be to plug a USB cable into the system and let it charge overnight. (I realize this puts the charging at 100mA max, but if need be we can look at other options such as a docking station to provide higher charging current.)

    We are still working on the total size of the enclosure but something like 5inches x 2 inches x 2 inches is the current goal.

    We would like the system to run for about 8-10 hours on battery and figure it draws on average 200mA.   (I'm still building the prototype so exact consumption values are estimates.)

    thanks,
    Bob

  • 0 in reply to Bob Shankle
    TI__Guru**** 166006 points
    Bob,

    USB ports are only limited to 100mA if you do not perform USB enumeration. Our chargers do not perform enumeration so you would technically need a USB chip to do that. That said, many of our customers seem to ignore that spec or use a vaguely worded amended to pull up to 500mA from legacy USB ports.

    I'm going to assume you use a single cell LiIon battery. Based on your requirements, you need a 2000mAHr battery at least. Charging overnight for 8 hours would require at least 2000mAHr/8Hr = 250mA charge current. You would use one of linear regulator based chargers for that low of charge current.
  • 0 in reply to Jeff F
    Intellectual 265 points

    Hi Jeff,

    Thanks for the feedback.  Can you point me to a reference design (schematic showing which TI chip to use and the supporting caps/ resistors and recommend battery?  I was having a hard time finding reference designs for 5V.  I have a working design using much lower voltage (around 4v.)

    thanks again,

    Bob

  • 0 in reply to Bob Shankle19
    TI__Guru* 75656 points
    Hello Bob
    The bq24040 may meet your requirements.
    It is a 5V linear charger that can be set to 100mA/500mA or up to 1A, minimum number of external parts.
    In addition to the Data Sheet and User's Guide see Quick start guide SLUA901.

    www.ti.com/lit/pdf/slua901
  • 0 in reply to Bill Johns
    Expert 1180 points

    Hi Bill,

    Thanks for the suggestion, is there a battery you recommend? (Preferably a DigiKey part number or some other vendor.)

    thanks again,
    Bob

  • 0 in reply to Bob Shankle
    TI__Guru**** 166006 points
    Bob,

    We typically do not recommend the battery. That said, commonly used and available battery in our forum is 18650. TI does have high level reference designs by end equipment, for example www.ti.com/.../overview.html and a reference design database that you can search by power requirements www.ti.com/.../index.html.
  • 0 in reply to Jeff F
    Expert 1180 points

    The 18650 was throwing me off because it says 3.7V on the battery.  Maybe I use a configuration of 2....

    I'll check the links.

    thanks much!

    Bob