• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 916 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.

BQ24133: Understanding charging and Heat Dissipation

BALAJI VENKATACHALAM
Prodigy 120 points
Part Number: BQ24133

Hi,

      I am trying to charge a 2S Battery (7.4V) with 2A charge current at 12V. The board is fabricated with 2Oz Copper. Below is the schematic of my battery charger section:

I have the following observations and questions:

  1.  I can see that the BQ24133 chip gets hot significantly. Is this a correct behavior?
  2. How do I calculate the heat dissipation of the BQ24133 using the thermal parameters in the datasheet for my charge current?
  3. I also see that the current consumption at 12V is around 1.72A, when the battery is at 7.4V (and never 2A). How is it explained?
  4. I see that the charge current consumption oscillates from 1.2A to 1.44A after about 10 minutes of charging. Is this correct behavior?

Regards,

Balaji.V

  • 0
    TI__Expert 8690 points

    Hi Balaji,

    In your previous post, the TS voltage was very close to the cold temperature threshold. Please make sure you have the correct values on the TS resistor divider, taking into account the thermistor being used. You can calculate it using the our tool: www.ti.com/.../sluc244

    To answer your questions:
    1. The bq24133 has integrated MOSFETs, and all power goes through our chip. It will have to dissipate the power loss through the thermal pad. Make sure that the thermal pad is connected to a GND pour with enough vias (look at the second to last page of our datasheet).
    2. You can look at this app note for more information: www.ti.com/.../spra953c.pdf
    3. What is the voltage at ISET and ACSET in this condition? How much is the input current from the adapter? The charger may be hitting input current limit regulation.
    4. Please provide a scope shot of PVCC, VSRN, SW and STAT when this happens.

    Regards,
    Steven