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simple Li-Ion Single Cell charger with power path function - recommendations?

Other Parts Discussed in Thread: BQ24278, BQ24253, LM3668, TPS61130, TPS61120, TPS55065-Q1, TPIC74101-Q1, BOOSTXL-BATTPACK, BQ24210, BQ27510-G2, TPS63001, TPS63002

Hello TI-Comunity,
            i am on the way to develop a small battery powered 'gadget' as a hobby project.
            and at the moment im searching for the right power management parts
            my requirements are
                Single Cell, Li-Ion / Li-Pol Battery, Capacity 1000mAh - 2200mAh
                for my system i need 300mA @ 5V and 200mA @ 3.3V
                the system must be powered during charging the battery
            i have searched the TI Website and found the following products
                    (selected with the help of the
                    BQ24278 2.5A, Single-Input, Single Cell Switchmode Li-Ion BATTERY CHARGER with Power Path Management
                    BQ24253 2A Single Input I2C/Standalone Switch-Mode Li-Ion Battery Charger
                    i think the Power Path Management is the thing i need for the 'charge while power system' requirement
                    i need a charge current of 0.5A up to maximal 2A -
                    so i can charge the battery with 0.5C or 1C - depending on the recommendation of the battery datasheet.
                    (for the battery i will choose the biggest one that fits in my housing (max 2200mAh) -
                    and the size housing will be defined as a compromise between system uptime and as small as possible
                    after i know how much board-space i need for all the components ...)
                        Adjustable, 90% Efficient SEPIC Converter with 200-mA LDO for 1-Cell LiIon or Dual-Cell Applications
                    i think i can use the internal LDO to generate my 3.3V Output - so i have less parts.
            i am new to powermanagment / Battery handling and would be glad to get some advice and tips
            i am on the right way with this parts? or is there some other appnotes or helping documents that i have not found yet?
            for this project the board-space is not limited in some way.
            more it is use full if the parts are hand-solder able.
            The Design - if the prototypes will work - will be mad as really small series for art projects-
            so its most likely (up to now) they will all be hand-soldered.
            if i have seen it right in the parametric search there is no chip with power path in TSSOP.
            there is a micro controller in the system, so it would be possible to use a charger chip with I2C
            but i would prefer a standalone solution.
            thanks for your time and help
            sunny greetings
            Stefan Krüger

  • Hello Stefan,

    Yes, to have the system powered when an adapter is attached even in the case of a dead battery selecting a charger with Power Path will make that happen.

    -What are you plugging this charger into? Will it be connected to a wall adapter or a USB port?

    We can work through narrowing the charger part search to the best option with this information.

    Yes, most of the battery charger ICs are found in CSP and QFN and both can be a challenge to hand solder.


    Looking at your power converter selection I would recommend looking at a different device. While the one that you selected is a single chip solution a SEPIC topology might be a difficult place to start if you are not familiar with power supply design also the LDO has a rated maximum at your expected 3.3V load current.

    -I would recommend using the TI WEBENCH tool. This is a great tool regardless of your power supply design experience. I would recommend going to the POWER SUPPLY ARCHITECT tool and place the voltage ranges that you are expecting which range from the lowest battery voltage you expect to the peak voltage you expect from the Power Path output. Then you provide your two rails, the 5V and the 3.3V and it will provide you with a number of options to work with. Here is the link, let me know if you have any questions:

  • Hello Ryan,

    thanks for your answer.
    as input i will have a wall adapter - so no limitations on this side.
    (sorry for forgetting to include this info.)

    i have tried the Webbench tool.

    if i go through the process and use this start values:
    VMin=3.0V VMax=5.5V

        5V, 0.3A
        3.3V, 0.2A

    the tools in standard Optimisation uses
    LM3668-4550    for 5V
    LM3668-2833 for 3.3V
    so the same Series for both-
    LM3668 1A, High Efficiency Dual Mode Single Inductor Buck-Boost DC/DC Converter
    its in an WSON ~3x3mm package.

    for me the webbench tool is to good at optimisation for board space ;-)
    i would like to have a easy system - so i have a small amount of external components -
    just out of the fact that than i have fewer points to be careful with the right parts -
    i said - its the first time i build buck/boost / converters - so much things to learn for me :-)
    the overall board-space is not so critical. so the parts can have 'big' cases.

    with the help of the parametric search i found that there is a similar part to the TPS61130 PW
    its the TPS61120 PW
    the nice thing about this is - it is available as TSSOP so easier to hand-solder :-)

    i have read through the datasheet and if i understand it right -
    it fulfills all my requirements.
        Figure.1 Boost Converter Maximum output current vs Input voltage (VO = 5V)
            page 8
            --> VI=3V, AO = 430mA
        Figure.5 Boost Converter Efficiency vs output current (VO = 5V)
            page 9
            --> VI=3.3V, IO = 400mA, Efficiency ~ 90%
        Figure.15 Maximum LDO output current vs LDO Input voltage (VO = 3.3V)
            page 11
            --> VI=5V, IO ~ 330mA
    the load in my requirements are my maximals -
    for my 3.3V rail in normal operation i will need about 30mA (the 200mA are the maximal in 'transmit' mode)
    so i can reduce the currents if the battery gets empty.
    (there is a uController to handle this.)

    so i hope you can give me some help / points why to choose which one -
    thanks for your help and time

    sunny greetings stefan

  • bq24253 is the best choice for the charger.

    Since SYS will always be below 5.0V, I don't think you need the SEPIC TPS61130.   You might consider the boost only TPS61120.  In either case, I would connect the LDO input to SYS output of charger.  

  • Hello Stefan,

    Regarding the power converter. If you are expecting to see the full voltage range from 3.0V to 5.5V I would advise against a SEPIC topology.

    You could look into the TPS55065-Q1 or the TPIC74101-Q1 to condition the wide input voltage to 5V and then select an LDO for the 5V -> 3.3V from the buck-boost or the SYS of the charger.

  • Hi Jeff,
    Hi Ryan,

    thanks for your suggestions.

    i have checked the datasheets of both chips.
    and found one question regarding both chips.
    at both chips the datasheet says on page 12
    'Extension of the Input Voltage Range on V(driver)' (Page 12),-205,719,-205,697
    it says that the minimum Voltage for start up must be 5V.
    so if my battery is maximum 4,2V this thing would only start if it is powered
    with an dc 5V from extern.
    after the start it can go down...
    i checked the TPIC74101-Q1
        Page 14 / Figure 5. Typical Input Voltage (V(driver)) vs Maximum Output Load Current (IO)
    so at my minimum VIn of 3V it can deliver ~600mA - thats fine -
    in the datasheet of the TPS55065-Q1 i cant find a Graph for this.

    what did you mean with 'Since SYS will always be below 5.0V' -
    have i missed something in the powerpath / charger chip datasheet?
    if my wall adapter is a little of i can get 5.5V,
    so if i have understand all right i would have this 5.5V at ma SYS line??
    for the LDO -
    if i connect this to the SYS path i would get a unstable 3.3V Rail
    if the battery drops below ~3.5V (3.3V + ~0.2V Dropout)
    and if i have understand the LiPo / LiIon technology right,
    then i would miss a lot of capacity if i shut down my system at 3.5V.

    i have found the Fuel Tank BoosterPack
        in the Users Guide there are schematics so i looked what this design used:
        Charger: BQ24210
        Gas Gauge: BQ27510-G2
        Buck-Boost for 3.3V : TPS63001
        Buck-Boost for 5.0V : TPS63002
    so if i base my design of the Buck-Boost section of this i just have to deal with
    the 'challenge' of hand solder the 3x3mm QFN.

    ok - i think - if i want to go with an 'state of the art' design of my power stage -
    i have to go QFN ;-)

    what is your opinion about the TPS63001 / TPS63002? do you like these ones?

    sunny greetings

  • All of the chargers mentioned above will provide an output that is below the input voltage.  The powerpath ICs provide a SYS voltage that is slightly higher than the battery regulation voltage (e.g. 4.2V + a few %).  The bq24210 provides up to 4.2V.

    TPS6300X are good choices for buck+boost. 

  • Hi Jeff,

    thanks for the explanation  - i missed this part..

    i will try this setup :-)

    thanks for all the help!

    sunny greetings