• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 62 subscribers
  • Views 323 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

BQ24725A: Chip & inductor temperature during charge.

Grigory Kozyakin
Prodigy 10 points
Part Number: BQ24725A
Other Parts Discussed in Thread: BQ40Z50-R1, BQ24725

Hello!

In our scheme we use bq24725a with the parameters "Charge current = 1472" and "Charge voltage = 16800". Input voltage = 23.7 - 24 V. Battery - 4 cells Li-Ion 3.7 V (4.2 V max) controlled by bq40z50-r1. The actual current flowing into the battery and reported by its controller is 1300 mA. Given the error of the DAC bq24725a this is normal. Circuitry is identical to EVM. L1 - WE-LHMI SMD Power Inductor, size 5030, 4.7uH (katalog.we-online.de/.../74437336047.pdf). Q4, Q5 - SI4946EY (www.vishay.com/.../70157.pdf).

What is the normal temperature of the controller and inductance at such a current and voltage? In our case, the inductance heats up to 70-80 degrees. bq24725 also has the same temperature.

Thank you.

  • 0
    TI__Guru 56650 points

    First, we need to estimate the IC and inductor power loss.
    1. The most IC power loss is for the switching FET gate drive circuit. If the high side switching FET Qg is Qg_hi and low side switching FET Qg is Qg_low, the gate drive circuit current consumption is 1/2 (Fs x Qg_hi) + 1/2 (Fs x Qg_low). After you have the power loss, you can use datasheet thermal resistance to estimate the temperature rise of the charger IC.

    2. Inductor loss estimation. Some inductor vendors support the inductor loss and temperature estimation. For example: https://www.vishay.com/inductors/calculator/calculator/