BQ24610 LODRV waveform

Hi Frank,

What mosfet is the customer using? They could try using one with a smaller Qg to reduce the damping effect.

Hi David,

I have recommended the customer to pallel a Cgs at the GS pin and slow down the turn off speed. And add a RC snubber at the low side mosfet. What's your comments about this? Thank you.

BR

Frank

Frank,

Can I see the LODRIVE trace with just the parallel Cgs, and then a trace with the parallel Cgs and RC snubber? That may work

Hi David,

I think it's caused by the Vds volatge quick change then influce the Vgs through the Cgd. Do you agree with my opinion? So my ideas should be helpful. And i also want to check why small Qd will helpful? Thank you.

BR
Frank

I think that it is definitely worth looking into. That very well may be the issue.

I suggested a fet with smaller Qg to reduce the gate charge. The waveform looks mildly underdamped, which can cause the bumps like that. Reducing Qg slightly should push the waveform to a more critically damped response.

EDIT: It appears as if you are on the right track Frank. Try adding 100pF to the Low Side Fet's gate to see if that works. You can also increase the BTST series resistor to see if that helps. Also, is it possible to get a waveform of the switching node?