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BQ25756: BQ25756 heating up coil

Karol Pelzner
Prodigy 10 points
Part Number: BQ25756

Tool/software:

Hello, 
I'm using BQ25756 to charge a 7-cell LFP battery. At the moment I'm doing tests with a DC power supply as the input. When the input voltage is within the range of 20-27 V (and 1 A of charging current) I can hear high-frequency switching noise and the coil heats up to around 100°C. I'm using NR8040T100M as the coil so the DC current shouldn't be a problem. What can be a solution here? 

  • 0
    TI__Mastermind 31085 points

    Hello Karol,

    I've got a few questions to help us debug this:

    • What's your battery voltage during this condition?
    • Does the inductor heat up less if you reduce the charge current?
    • Does the inductor heat up less if you replace the inductor with an inductor with a lower DCR?
    • Does the circuit behavior improve if you set EN_PFM=0?

    I'm looking through the inductor datasheet and I see it has a typical resistance of 34mΩ. At the moment, I think reducing the inductor's DCR will improve the circuits behavior.

    Best Regards,
    Ethan Galloway