Hi team,
My customer is developing a circuit converting 24Vin to 5Vout with LMR14020. They made 8 boards for test but found 4 boards of them have normal 5V output but the other 4 boards have a abnormal 2.4V output. We measured the SW of the good board and bad board. please see below picture for the SW waveform.
The left one is the good SW waveform and the right one is the bad SW waveform. In the bad SW waveform, the high level is 24V but the low level is -7V instead of around 0V.
What's more, we also measured the Vin,EN,SS pin of the bad board. The Vin and EN are normal which is 24V. But the voltage of SS pin doesn't ramp up when the board is powered on.
Do you have any advice on why the SS pin and SW pin have the issue? I also checked the customer's PCB. The ground side their Css and lower divider resistor are connected directly to the power GND instead of the pin 7. Do you think the poor PCB layout would cause the above issue？ Thanks.
Best regards,
Wayne
