LM5117: Chip damage under switching action

user5149236

Part Number: LM5117

The output is loaded with 5A, switch input power (24V or 50V), it is prone to chip damage.
The circuit that outputs 5V does not have this problem, but the circuit that outputs 12V can happen easily.
How can I solve it?

The circuit is basically designed according to WEBENCH.
When debugging the 12V output, it was found that the faster the frequency is, the lower the load capacity is, so the RT is used at 10K.
No load start chip circuit, 12V output is normal, then load 5A for 8 hours test, can all run normally.

I tried to adjust the parameters, but found that the load capacity is weaker, I do not know if it is layout problem.

Best Regards,

Steve Wu

over 7 years ago

0 Timothy Hegarty over 7 years ago

TI__Guru 72732 points

Hi Steve,

Please forward the schematic and layout.

Regards,
Tim

0 user5149236 over 7 years ago in reply to Timothy Hegarty

Prodigy 20 points

Hi Tim，

The layout file will be posted later

Regards,
Steve Wu

0 Timothy Hegarty over 7 years ago in reply to user5149236

TI__Guru 72732 points

Hi Steve,

R13 is 5mOhm corresponding to a ~24A current limit (120mV), yet the inductor is only rated for 9.3A.

If this is such a high-current design, you also should consider a lower RDSon low-side FET.

Also, I advise using ceramic input capacitors (e.g. 2.2uF/100V/X7R/1210). The electrolytic cap provides minimal filtering at 470kHz (RT = 10k) and is mostly used to provide input filter damping. Most important is to position the ceramic input caps as close as possible to the MOSFETs.

Regards,
Tim

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LM5117: Chip damage under switching action