Good morning,
I have this product into our SMPS used to lower a 24V DC input down to 3.3V, 1A average load. The IC is externally clocked / synchronized to a supervisor microcontroller which also checks for the proper functioning of other supplies on the board, synchronization frequency is 606KHz.
After 3 years, I'm are getting some faulty units back and I noticed that the microcontroller starts the ADP2443 then it switches it off almost immediately because it cannot keep the output voltage properly at 3.3V, then it keep retrying indefinitely, but it cannot start correctly.
I also noticed that heating the IC makes it to function almost correctly for some time, while freezing make it to work very badly. I then bypassed the supervisor microcontroller to force the ADP2443 on and here's what I got:
Yellow trace is the SW output going to a 6.8uH inductor, the purple trace is the output voltage: the IC is not working properly at all, but the things are worsen when
freezing it slightly and here's what happens. Voltage rises up to about 4V then PWM stops then it starts again.
If the IC is replaced with a new one, correct and stable operation is restored, no matter if it is heated or frozen.
In your opinion, what could be the cause of this failure ?
When output voltage begins to rise, there are strong (-10V) negative pulses on the SW output, just like if the output mos switching to ground isn't working properly.
Can we modify the circuit to prevent this failure in future ? Is there anything else could we check ?
Many thanks.
