MP4575 48V input issue

DC-DC Power Converters
1

Hi, I am using 2 DC/DC MP4575 on my PCB.

One converting 48V to 5V and its enable pin is controled by a uC (with no resistor linked to Vin) and another converting 48V to 24V with a 1MOhm pull-up resistor connected between Vin and EN.

First one is always working but the second one“burns” when the Vin power supply is too high (really approximatively about 42V, which is still below the absolute maximum input value (55V)).

Even if the pull-up resistor value is enough to limit the inside clamping diode current, do you think in some case the voltage would be still too high ?

A second hypothesis is that there is an external bootstrap diode (linked between BST pin and regulated output) for both converters while I shouldnt mount it for the 48 to 24V converter because the output voltage is too high (24V instead of the “3V-5V rail” as defined into the datasheet).

Thank you in advance for your reply,

2

Hello, apologies for the delay in our response on this request.

Do you have a schematic that you can share here? I would be interested in taking a look and seeing if there is something wrong here. I agree this is within the voltage spec here so perhaps this is worth reviewing.

I know it has been some time since your initial post, so if there have been any updates, do let us know.

Best,

Krishan