• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 2 answers
  • Subscribers 63 subscribers
  • Views 1063 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.

BQ51050B: Operation at low charge currents

Derek
Mastermind 9792 points
Part Number: BQ51050B
Other Parts Discussed in Thread: BQ51013, , BQ25100, BQ51003

I'm working on a small wearable project where PCB area is very precious and we'd prefer a one-chip solution vs. two-chip solution. Battery is a coin cell with nominal charge current of 40mA. I saw that the BQ51050B isn't recommended for charge currents below 500mA so we would need to go with a bq51013 + charge IC. Can we do this with the bq51050? Is it that the current regulation is poor below 500mA, or is there another reason?

Also, if you're working on the product line I recommend having a version that supports low charge currents and/or that incorporates a low-Iq buck converter too to reduce component count.

  • 0
    TI__Guru* 75886 points
    Hello
    For 40mA I would recommend the BQ51003 + BQ25100 for best performance.
    The BQ51050B will lose accuracy at low charge current. This could lead to early termination of charge or NO termination then timer fault.
  • 0 in reply to Bill Johns
    Mastermind 9792 points
    Does this apply for any current below the 120mA (Itermination, min) parameter? For example if we were ok charging at 80mA could we use BQ51050 or same answer?
  • 0 in reply to Derek
    TI__Guru* 75886 points
    Charge at 80mA should work. Problem will be termination which is typically 10% of charge current or 8mA. We have been recommending termination above 30mA set point.
  • 0 in reply to Bill Johns
    Mastermind 9792 points

    Thanks - also I recommend that TI investigate market feasibility of a BQ51050 that supports lower charge currents, like 400mA or less. Ideally it would have a powerpath too.

    Most of these wearable products end up with a lot of space just for power. More integration is desired. Five main categories:

    • Wireless Receiver
    • Fuel Gauge
    • Protection IC (since the batteries are tiny and usually don't have this)
    • Charger
    • Low-Iq Buck Converter

    I saw that the TPS25121A combines the last two, which looks appealing. Also nice that its I2C to make configuration easier, but with reasonable defaults. If you can combine all three of the main functions (wireless + charger + buck) then that would be fabulous. Basically a PMIC for wearables.

    Also, on an unrelated note, all the battery protection ICs need a separate dual FET IC - this should be built into the fuel gauge IC.

  • 0 in reply to Derek
    TI__Guru* 75886 points
    Thanks for the feedback / ideas, will pass the info on.