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BQ24133: Some questions in the datasheet

Yue TANG
Expert 8695 points
Part Number: BQ24133

Hi,

I got two questions from  my customer as below:

Q1: from the BQ24133 datasheet, as below capture, need to add external Cgd and Cgs  to decrease the turnon speed. so, do I need to add some circuit to release this energy of these external Cgd and Cgs?

Q2: Some mature circuit added R14 and C17 at BTST pin. could you please suggest what is this for? thanks. 

  • 0
    TI__Guru**** 165766 points

    Yue,

    Regarding 1, the CMSRC pin is the return for the charge pump output at ACDRV.  No additional circuitry is required to discharge the capacitors.

    Regarding 2, R14 and C17 form an RC snubber to damp the ringing at the SW node that can cause EMI. Both the resistor and capacitor must be empirically sized/tuned per board layout, i.e. the size of each is dependent on board layout.  You will lose some efficiency (~1-2%) with the snubber.

    Regards,

    Jeff