Short circuit condition with LM5116

simone frasanni

Other Parts Discussed in Thread: LM5116

Hi to all !
I'm in trouble with LM5116 during short condition : when I apply a shortcircuit in the output, the LM5116, and the mos low side they break both.

These are my features :

Vin=30Vdc

Vout=12V

Lout=22uH

Cout = 3x220uF

Fsw=200kHz

Rcs=10mohm

The input power supply is limited to 4Amax and the low side and high side mosfets are about 50A.

Does someone have some ideas about this ?

Thanks in advance

over 9 years ago

0 Garrett Roecker over 9 years ago

TI__Mastermind 21720 points

Simone,

Can you send a wavefrom of the switch node when you short the output voltage? This may help to track down the issue.
Also, is the LM5116 configure to operate in diode emulation mode?

Thanks,

Garrett

0 simone frasanni over 9 years ago in reply to Garrett Roecker

Intellectual 285 points

Hi Garret, thanks for your cooperation.

LM5116 works in diode emulation mode : Rdemb=10k, while Rsense is 10mohm .

Follow there are the waveforms in shortcircuit condition : CH2 = UVLO pin ; CH1 = switch node; CH3 = Iout (10A/div)

0 Garrett Roecker over 9 years ago in reply to simone frasanni

TI__Mastermind 21720 points

Simone,

The waveform you sent looks correct. The IC experiences an over current limit event for approximately 256 continuous switching cycles which results in the UVLO pin being pulled low. When this happens it is called hiccup mode and is intended to keep the power train from overheating.

Are you blowing up the low-side FET every time the output is shorted? What is the part number for the selected MOSFET.

Thanks,

Garrett

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Short circuit condition with LM5116