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BQ51050B: BQ51050 : End of charge never detected

sg_34
Intellectual 500 points
Part Number: BQ51050B

Hi

I've a build prototype for wireless charging based on BQ51050, where Ibulk is around 360mA (R14 = 670Ohm). Everything is OK, end of charge is detected, charge stopped at the end when my current reach the limit 10% of Ibulk, because my resistor Rterm is 2.4K.

Transmitter and receiver are OK and working well

For the production, battery is different and current Ibulk must be around 166mA : I just modify resistor value R14 = 1.74kOhm (as on schematic attach) to reach the current required

Charging is OK at 166mA, but when Ibat decrease, Ibat never stop, charger never stop : TX OFF conditions never detected and I don't understand why?

Do you have an idea of what can happen? is there specific value, current or voltage to check during charging to understand what happen?

Thanks for your help

  • 0
    TI__Guru 67836 points
    Hi
    The bq51050 was designed with a 1A charging current with higher termination currents in mind and it works well in this condition.
    With lower termination current the accuracy becomes an issue. It is possible for low current such as 16mA that the actual termination current will be much lower. If a system load is present unit may not reach termination point.
    Recommend moving the termination current above 40mA.
  • 0 in reply to Bill Johns
    Intellectual 500 points
    Ok, thanks a lot, I'll modify R16 to 5k62 Ohms

    Is there oter components (BQ family) recommanded for lower current? I'm working on a new design where charging current will be around 0.1A?

    Best regards
  • 0 in reply to sg_34
    TI__Guru 67836 points

    Take a look at TIDA-00318.

    This is a two chip solutions the bq51003 is designed to work well at low power and the bq25100 is designed to work well with small Li-ion batteries.