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bq24172 emc problem

asher sela
Prodigy 90 points
Other Parts Discussed in Thread: BQ24172

hi

i am using the bq24172 charger and i have emc issue. i want  to expande  the rise time of the charger,can you advice a recomended change schem.

remark - i used a resistor value 50 ohmes in series of 47nf  capacitor at pin btst in order to expand the rise time but it seems that the freq at this pin is not

stable,does it correct? the rise time after the change become appx  100nsec.

* Battery voltage (VBAT) -12.6v

  •   * Input current (IIN) and voltage (VBUS) - 3 amp,12volts
  •   * System voltage (VSYS) and current (ISYS) 14v /2amp
  •   * Charge current (ICHG) - 2 amp

thankes

  • 0
    TI__Genius 11480 points
    Hi Asher,

    Is there any chance you mixed up the system voltage and input voltage? You should not be able to charge a 12.6V battery from 12V with a buck converter.

    Many EMC/EMI issues can be resolved through layout and PCB design. If you want me to take a look at yours and offer feedback, I would be happy to help.

    With the bq24172, the switching FETs are integrated, which makes it impossible to add a gate resistance or extra Cgs to slow down switching. If you are against altering the layout, I would suggest adding an RC snubber at the SW node.