Hello!
We designed a C6678 board following the standard EVM6678 board, and all schematics of UCD9222 + UCD7242 are the same. However, we have debugging this part for almost a month. Can someone help me analyze why this error exsits?
Here are some shortcuts of our waveforms and results:
1. Reports from Fusion Digital Power Designer. UCD7242 reports FLT error, and there's no pwm output.
2. When we remove the output inductor, the duty cycle of pwm rises to be approximately 98%, and the output now is 12V with heavy noise.
3. We then add the inductor and remove all output capacitors except a 330uF one, and the output now is averagely correct but still with heavy noise. I am sure that 6678 cannot work under this voltage.