Other Parts Discussed in Thread: LM5146DESIGN-CALC
Hello,
We are using following circuit with components as given in it and we have some audible noise on pcb (capacitors) at light load conditions.
NOISE:
Output voltage: Measurements shows that DCM causing +/- 50mV output ripple at around 8 kHz frequecy and ceramic capacitors producing some audible noise.
Ripple Generation Method
After some investigation we have found out that our CB capacitor value is not correct.
But LM5146DESIGN-CALC design tool shows 56pF. Is design tool giving wrong values?
Changes:
We have changed CB as 220pF and CA as 3,3nF and measured the output again.
Now output ripple is around 20mV and there is no audiable noise on pcb.
Switching:
But switching seems to be not normal. There is some spikes between t_on phases.
Is this switching behaviour normal?
Could you please also confirm that changed capacitor values (3,3nF and 220pF) won't cause any problem.
Thank you for your support.