LMR14203: FAILURE MODE

Gabriele,

I can help diagnose an issue with your design if that's what you're after. Please share details on the failure, the schematic, layout, and any scope shots that help show the issue.

-Sam

Hi Samuel.

You can see the schematic in the picture below.

The TVS DT1 is bidirectonal TVS (the symbol is incorrect).

This power supply block is used in automotive system with alternator circuit.

In some cases I have found the following problems:

- the diode 1N4148 are opened

- the capacitor C1 are shorted or low impedance (about 2 or 3 Ohm)

- the LMR14203 have internal mosfet drain-to-source shorted

The power supply range is 10V to 32V.

What could be the issue?

Voltage spikes on power supply line?

I don't know how it is possible that the internal mosfet have drain-to-source shorted.

BR,

Gabriele.

Gabriele,

Absolute Maximum rating of VIN is 45V. This is an alternator circuit so I assume this input sees load dump conditions. Check worst case to make sure none of the pins (mostly VIN) are exceeding abs max.

-Sam

Thanks for your answer, Samuel.

I will investigate about load dump conditions.

However I would like to understand how it is possible to LMR14203 have the internal mosfet drain-to-source shorted.

How can that the drain-to-source channel shorting?

Can the voltage spike to VIN pin (E.g. Load Dump, ...) short the channel? I thought that cause a drain-to-source channel opened, not shorted.

Gabriele,

If a device breaks, it's usually due to violating abs max. Depending on the conditions of the overvoltage (how much voltage, how much current, how long...) we can see an open or a short failure mode.

-Sam

Samuel,

I think the mosfet channel goes to short-circuit with high current and goes to open with high voltage.

Is it correct?

Do you think is it possible with either voltage spike or continuative voltage above abs max?

Gabriele.