• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 63 subscribers
  • Views 420 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.

BQ25050: Suitable Battery charger with power path feature

Sai Ram S V K S
Prodigy 70 points
Part Number: BQ25050
Other Parts Discussed in Thread: BQ24072, BQ25616

Hi,

I am searching for a battery charger with power path. I am upgrading my client application which was a standalone application with main power supply as a 3.7V 8000mAh battery.

The current requirements are as below:

1) The battery is charged using 5V coming from another board through a 3m cable. This power is always provided to the application.

2) In case of some power failure on 5V rail, the 3.7V Li-Po battery provides power to the system. It is the same 8000mAh battery as described above(the previous design used 2A as charging current in the constant current phase). The client is not particular on the charging time of the battery.

3) The application load is not more than 1A and the output voltage should be between 3.6V to 5V.

So, based on the above requirements, I selected BQ25050 since it has a power path feature as well as supplement mode.

Can you please advise me whether the selected part (BQ25050) is appropriate for this application. What would be the thermal impact (the 8000mAh battery doesn't have another pin for temperature measurement) on this part if the battery is charged from very low voltage at 1A, since it would take a lot of time for it to get fully charged.

Please suggest other parts for this application. Thanks

Best Regards,

Sai Ram

  • 0
    TI__Mastermind 31810 points

    Hi Sai,

    Based off thermal calculations and the 1A charge current spec of the BQ25050 another part is probably more appropriate. When the battery is discharged the required power dissipation is (5v-2.9v)x 1A = 2.1 W and the max allowable power dissipation before temperature regulation lowers the charge current is 1.7 W, which can be found in the data sheet and is calculated using RthetajA and the maximum junction temperature. The battery would therefore charge at a slower rate until its voltage rises. The 1A current limit also poses an issue when you are attempting to charge the battery at 1 A while the load is being powered.

    An alternative linear charger option is the BQ24072, but a switching charger is probably a better option for your application. A potential option with power path is the BQ25616.

    Best Regards,
    Garrett

  • 0 in reply to Garrett Kreger
    Prodigy 70 points

    Hi Garrett,

    Thanks for your quick reply and suggestion. I selected BQ25050 since the application(the application is a smart lock used in bicycles) requires very little load current (less than 100mA, the peak current may be above 500mA due to stall current of miniature DC motor) and the system voltage should be between 3.6V and 5V for proper operation of the system, so the design would be such that battery voltage can't be less than 3.7V at all times. But the main concern was the thermal dissipation resulting in charging the huge 8000 mAh battery and as you suggested it might be problematic.

    I will consider BQ25616 as you suggested and it is a better alternative compared to BQ25050. But I have a concern about whether the switching noise will affect the BLE performance? The board size would be around 60mm x 40mm.

    Awaiting your reply.

    Thanks & Regards,

    Sai Ram

  • +1 in reply to Sai Ram S V K S
    TI__Mastermind 31810 points

    Hi Sai, 

    There will always be some amount of noise with switching converters, but the affect it has on performance really comes down to the sensitivity of the other components and the layout of the board. Based off your last response stating the load normally requires around 100 mA and that the battery will not be less than 3.7 V I think a linear option will work for your application, especially if you do not want any concerns about switching noise. Not letting the battery discharge past 3.7 V will also help the thermal dissipation. 

    Based off all this I would recommend the BQ24072 due to its 1.5 A charge current, but the BQ25050 you initially selected will also work. 

    Regards,     

    Garrett Kreger

  • 0 in reply to Garrett Kreger
    Prodigy 70 points

    Hi Garett,

    Thanks for your reply. I will consider your suggestion.

    Best Regards,

    Sai Ram