MP2322GQH-Z damage when used in cascade with isolated converter

DC-DC Power Converters
1

Hi,
I’m using MP2322GQH-Z converter to obtain 3V3 isolated voltage from an voltage input of 12V isolated from Converter DPAN02B-12 (Meanwell). MP2322GQH-Z is configured according to design of EV2322-D-00A.
DPAN02B-12 converter is dual, and its 12V output is connected to MP2322GQH-Z input. After several startups, MP2322GQH-Z is damaged providing an output of 0V. When normal operation, output is 3.1V.

DPAN02B-12 output can deliver 83 mA and I’m not sure if this value is very low enough to make to fail the MP2322GQH-Z in case of high current demand.

Additionally, I’m connecting the EN pin to input voltage (12V) using a 100kohm according to reference design in EV2322-D-00A. In datasheet, EN rising threshold is 1.2V. Is my connection correct? Should I use a voltage divider instead?

Finally, as the inductance I’m using B1047AS-680M=P3 (Murata) instead of 744314330 (Würth) of eval board. B1047AS-680M=P3 (Murata) provides higher DC resistance than 744314330 (Würth). Could this situation impact on the output voltage ? Should I use the Würth inductance?

Thank you in advance

2

I forgo to detail that the design is for 1A, but it is consuming 0.1A. Could be the inducante low enough?

3

Please, could anyone help me with my question?

4

Hello @almudena.martinez ,

From what I understand, you have a 12V rail which is then isolated via the DPAN02B-12, and then that isolated 12V is fed to the MP2322?
If the isolator can only provide 83mA, then the MP2322 can only provide about 300mA out (assuming 100% efficiency). Perhaps what is happening is when the MP2322 wants to provide more than 300mA demands more current from the isolator which then turns off the isolator and now the MP2322 has no input voltage?
As for the inductor, as long as the rated current and saturation current are at least 20% larger than the expected max current, you should be fine. Higher DCR would lead to less efficiency, but generally you want to make sure the inductance does not drop too much during all expected current ranges.
Hope this helps!

Regards,
Jonathan

5

the other issue is just connection the EN pin to the 12V input means that the converter will turn on at a very low voltage potentially crunching the isolated power supply. I would suggest setting up the converter to turn on once the isolated converter reaches 8V or so.