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BQ51050B: Can not reach a charging current of 500mA.

Vivien BDZ
Prodigy 20 points
Part Number: BQ51050B

Hi,

I am currently trying to improve the charging feature of my PCB. Today my charge is set to 230mA as specified in the battery specifications (capacity of 1150mAh, standard charge current of 0.2C) but I need to accelerate it to 500mA (half of the max charge current which is 1C).

My schematic is the next one:   .

Before changing the R137 I measured a charge current of 200mA which is compliant with the set limit (240mA), minus the current consumption of my Board (40mA). I changed R137 by a 430 Ohm resistor and the maximum charge current limit I reach in my tests is 385mA. This measure is not what I expected (385mA + 42mA is different from 500mA).

During my tests, I use a discharged battery at 3V. At the wireless charge beginning, I measure VRECT, IBAT and VBAT: VRECT = 5V, VBAT = 4.08V and IBAT = 385mA.

Do you think the BQ51050B difficulties to reach 500mA are due to the coil? Or the schematic?

In advance, thank you for your support. Best regards.

  • 0
    TI__Guru 67866 points

    Hello

    I suspect the problem is the coil, 760308101309.   The coil is 10uH and 26mm round, L value is low for a  small coil.  Recommend testing with a larger coil to confirm, 760308103202, 48mm X 32mm and 12uH, or TDK WR222230-6M8-G, 22mm round and 27uH.  

    As the coil size goes down the L value increases to compensate.