Other Parts Discussed in Thread: UCC28780
Hi,
My customer is working on power supply unit and uses PMP30720 as a reference, they faced the same problem with their design and with our reference design.
The problem is with the operation of the power supply based on UCC28780 at a negative temperature of -40 degrees.
The power supply does not start up. Pulses do not generate at pin 4. The reference voltage is 0V at pin 16.
18.5V is setting on pin 1 and maintaining until the board warms up to -5 (C).
In normal operation mode the voltage changes from 18.5V to 15V with a slight dip during the start.
They see the same behavior with our board - PMP30720.
If they firstly apply power to the power supply at +25 (C) and then cool it down, then the power supply works normally without shutdowns.
The question is what is the reason of such behavior of the UCC28780 at the start up at negative temperatures and how to fix this problem?
Thank you,
Daria