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

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.

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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:

http://www.ti.com/lsds/ti/analog/webench/power-architect.page

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

LOAD_1
    5V, 0.3A
LOAD_2
    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.
http://www.ti.com/lit/ds/symlink/tps61120.pdf#page=8
    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.

@Ryan
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)
http://www.ti.com/lit/ds/symlink/tps55065-q1.pdf#page=12&zoom=auto,-205,719
http://www.ti.com/lit/ds/symlink/tpic74101-q1.pdf#page=12&zoom=auto,-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.

@Jeff
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
    http://www.ti.com/tool/boostxl-battpack
    in the Users Guide there are schematics so i looked what this design used:
    (http://www.ti.com/lit/pdf/slvua32)
    
    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
stefan

Hi Jeff,

thanks for the explanation  - i missed this part..

i will try this setup :-)

thanks for all the help!

sunny greetings

stefan