LM5119: Chip shut-down

York Chung

Part Number: LM5119

Hi,I am a student in China. I have chosen LM5119 as my control chip in an interleaved buck circuit. The driving waveform (square wave) can maintain about only 10 seconds or even longer. Then the waveform disappears ,but the level of VCC is still 7.6V. This happened in the case of no-load and open-loop.

Please tell me why. Thanks a lot!

Tell me your e-mail if you want to know more about my circuit.

My e-mail: zhongshanyu@nuaa.edu.cn

over 7 years ago

0 Timothy Hegarty over 7 years ago

TI__Guru 58072 points

Hi York,

This could be a bad solder connection.

Can you provide your schematic?

Regards,

Tim

0 York Chung over 7 years ago in reply to Timothy Hegarty

Prodigy 100 points

Hi Timothy,

Thanks for your reply.

INTERLEAVED BUCK.PDF

That's my schematic.

0 Timothy Hegarty over 7 years ago in reply to York Chung

TI__Guru 58072 points

Hi York,

Is the input voltage above 65V? I see you have a resistor divider to the VIN pin and external isolated gate drivers. This is a non-standard implementation.

Regards,

Tim

0 York Chung over 7 years ago in reply to Timothy Hegarty

Prodigy 100 points

Hi Tim,

Thanks for your reply.The input voltage is about 60V.The schematic I sent to you is original version. I have changed the value of R2 into 1Ω and removed R4.

If there are no external isolated gate drivers and connect the chip to the buck circuit directly, the voltage of pin 'SW1' and 'SW2' may exceed the 75V which is the absolute maximum rating of this chip. So, I added external isolated gate drivers. And the external isolated gate drivers can generate drive signals normally.The question is that the drive signals(both the chip and the gate drivers) can only maintain for about 15s as I said before.

I can not figure out why this happend. I will be grateful to you, if you can solve this problem. Thank you!

York

0 York Chung over 7 years ago in reply to Timothy Hegarty

Prodigy 100 points

Hi Tim,

I have been thinking and trying to solve the problem I mentioned above these days, but there is no progress.

Have you ever thought of this problem? Could you tell me your opinion? I really look forward to your answer.

Regards,

York

0 Timothy Hegarty over 7 years ago in reply to York Chung

TI__Guru 58072 points

Maybe you can test a standard configuration without the external gate drivers. With careful MOSFET selection, PCB layout, snubber design, etc., it should be possible to keep the SW voltage below 75V.

Regards,

Tim

Power management

Power management forum

LM5119: Chip shut-down