flote21
Advanced Member level 1
Hello guys! I am wondering about the next issue:
I have used the next part of Monolithic Power to design the first stage of my power supply tree: MPQ4470A. Here you can see the schematic design of the part:
When I drive 24V to the input of the MPQ4470A, I get at its output 12V. However when the temperature increases, the output increases step by step until 24V. So when Ta=25 ºC Vout = 12V. But when Ta=70ºC Vout = 24V.
I have a PCB V1.0 where the sw regulator works fine. The only difference between my current PCB V2.0 and V1.0 is the output inductor L3. The PCB layout and the layer stackup is exactly the same. I have exchanged the inductors of V1.0 and V2.0 and PCB v1.0 works fine with both kind of inductors but V2.0 does not work fine with whichever inductor.
Finally I got a proper working of the sw regulator on PCB V2.0 making a short circuit L3. Then, the sw regulator works fine at whatever temperature. But I can’t figure out the reason of that behavior, and it is not a good solution because the output ripple is very large.
Anyone has an idea about what could it happen?
Thanks in advance and greetings.
I have used the next part of Monolithic Power to design the first stage of my power supply tree: MPQ4470A. Here you can see the schematic design of the part:
When I drive 24V to the input of the MPQ4470A, I get at its output 12V. However when the temperature increases, the output increases step by step until 24V. So when Ta=25 ºC Vout = 12V. But when Ta=70ºC Vout = 24V.
I have a PCB V1.0 where the sw regulator works fine. The only difference between my current PCB V2.0 and V1.0 is the output inductor L3. The PCB layout and the layer stackup is exactly the same. I have exchanged the inductors of V1.0 and V2.0 and PCB v1.0 works fine with both kind of inductors but V2.0 does not work fine with whichever inductor.
Finally I got a proper working of the sw regulator on PCB V2.0 making a short circuit L3. Then, the sw regulator works fine at whatever temperature. But I can’t figure out the reason of that behavior, and it is not a good solution because the output ripple is very large.
Anyone has an idea about what could it happen?
Thanks in advance and greetings.