LM5010: short circuit destroys device

Jan Bock

Part Number: LM5010
Other Parts Discussed in Thread: TPSM365R6

Hey team,

can you please help:

We continue to use the LM5010MH/NOPB HTSSOP14 regulator in a redesign.

If this is short-circuited at the output p24V to GND and the short-circuit is removed again, we destroy the regulator.

In the previous design this was possible without any problems, after the short circuit the controller started up again. The layout and component values are identical in the redesign. (Minimal manufacturing-related deviations in the layer structure)

Our assumption is that in the event of a short circuit via C121 and C120, we generate a negative voltage pulse at the feedback, which destroys the internal protective diode at the feedback.

The controller is also very susceptible to ESD.

Does TI have any information on the phenomena described?
How long will the regulator still be available, as a newer version TPSM365R6 is advertised on the homepage, which unfortunately is not footprint identical?

thanks

Jan

over 1 year ago

0 EricLee over 1 year ago

TI__Guru 58171 points

Hello Jan

1. Since the device shouldn't be able to start up if the device was damaged when the P24V node is pulled down to ground, I think the device was damaged during the restart. Would you please share some waveforms including SW and inductor current during the restart ?

2. Sorry I don't have any information about TPSM365R6 . Please create a new post if you have a question about this device.

-EL

0 Andreas Mangold over 1 year ago in reply to EricLee

Prodigy 40 points

Dear Eric,

see our meassurments in the PDF-file.LM5010_short_circuit.pdf

0 EricLee over 1 year ago in reply to Andreas Mangold

TI__Guru 58171 points

Hello Jan

It is hard for me to find the root cause of the damage based on the waveforms. Since the device got damaged after soft-short but works well after hard-short, I think the FB pin damage is not the root cause of the problem. Can you show me the circuit generating P12V? Also, the circuit including L23 if possible?

-EL

0 Andreas Mangold over 1 year ago in reply to EricLee

Prodigy 40 points

Dear Eric,

see the pictures of the wanted schematics.

0 Andreas Mangold over 1 year ago in reply to Andreas Mangold

Prodigy 40 points

0 Andreas Mangold over 1 year ago in reply to Andreas Mangold

Prodigy 40 points

Initially, the module survived several full short circuits with a relay contact without damage.
The circuit board then failed in the event of a loose, bouncing short circuit with open cable ends.
I was able to record the fault with the oscilloscope.
The channel assignment of the following oscilloscope plots is as follows.

CH1: VIN (48V)
CH2: Vout (24V)
CH3: Switch Node (Kathode V23)
CH4: IntVcc(nom. 7V)

Initial Short

first restart:

it is noticeable that the switch node does not reach the input voltage.
In addition, IntVcc drops to approx. 5V.
Could the path be partially short-circuited via a saturated choke? In other words, could the mosfet or bootstrap diode be damaged?

restart complete

complet measure

0 EricLee over 1 year ago in reply to Andreas Mangold

TI__Guru 58171 points

Hello Andreas

It is possible to damage the device if the converter operation follows this sequence,

VCC voltage falls down ==> BOOT capacitor voltage drops down ==> High-side MOSFET is not fully enhanced ==> SW node does not reach the input voltage / Voltage drop across the MOSFET is large ==> Excessive power loss on the high-side MOSFET when current flows (P=V*I) ==> Device damage.

If possible, please connect an 8V battery at the p192 node through a diode and retest.

-EL

0 EricLee over 1 year ago in reply to EricLee

TI__Guru 58171 points

I am closing this thread since I have not heard from you for sometime.
If you are still trying to resolve the issue, please feel free to open a new thread. Thanks
- EL

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LM5010: short circuit destroys device