LM5069: LM5069 My issue is power adapters can spark when plugged in due to inrush current

Lawrence He

Part Number: LM5069

Dear,

our client use LM5069, but we find the some issue, power adapters can spark when plugged in due to inrush current, so we need confirm schematic and calculator tool.

PS-1, in schematics, now the U32=NI and R831=0.

PS-2, Tried change C317=4.7uf but no help.

mx310hd-v03-13.pdf

and attached is our Design Calculator file. (ps, step-3 and step-4 more items don’t know what is it, so attached MOSFET datasheet

LM5069_Design_Calculator_REV_C-Jeff.xlsx

If any suggestion, Please advise me.

Thanks,

Best regards,

Lawrence.

over 6 years ago

0 Rakesh over 6 years ago

TI__Guru** 105361 points

Hi Lawrence,

Thanks for the details. Can you share test waveform of Vin, Input current, Vout, Gate during adapter plug-in event.

Best Regards,
Rakesh

0 Rakesh over 6 years ago in reply to Rakesh

TI__Guru** 105361 points

Hi Lawrence,

Can you provide waveform to understand the issue.

Best Regards,
Rakesh

0 Lawrence He over 6 years ago in reply to Rakesh

Genius 3280 points

Hi, Rakesh

we will update to you soon...

Thanks,

Best regards,

Lawrence.

0 Lawrence He over 6 years ago in reply to Lawrence He

Genius 3280 points

Hi, Rakesh

Regarding Vin, Vout, Gate during adapter plug-in event waveform please refer following, (C1=input, C2=output and C4=gate) and the Input Max. current I captured is 118mA.

As above figure, the Gate signal about 30V is could normal?

If any suggestion, Please advise me.

Thanks,

Best regards,

Lawrence.

0 Jeff Hsu over 6 years ago in reply to Lawrence He

Prodigy 90 points

Hi, Rakesh,

One more question, the gate voltage to 3x voltage is fine or not?

Regards
Jeff

0 Rakesh over 6 years ago in reply to Lawrence He

TI__Guru** 105361 points

Hi Lawrence,

Thank you for the test waveform.
You mentioned max input current as 118mA. This low level current should not cause spark when the adapter plugged-in. Did you able to capture peak current value using current probe?
GATE voltage will be Vin + 12V. So, 30V is correct.

I suggest to decrease the power limit, timer cap values and check. Make R830 = 18 K, C317 = 100 nF and test.

Best Regards,
Rakesh

0 Rakesh over 6 years ago in reply to Jeff Hsu

TI__Guru** 105361 points

Hi Jeff,

During normal operating condition the gate voltage will be approximately 12 V above IN/OUT.
Under which condition, do you expect 3x voltage for GATE?

Best Regards,
Rakesh

0 Jeff Hsu over 6 years ago in reply to Rakesh

Prodigy 90 points

HI Rakesh,

Thanks, tried R830 = 18K and C317 = 100nF but no help.
Also sorry, my current probe is bad now, so before 118mA is captured by multimeter.

Regards
Jeff

0 Rakesh over 6 years ago in reply to Jeff Hsu

TI__Guru** 105361 points

Hi Jeff,

It would be helpful if you somehow manage to capture input current during hot-plug event to understand where we stand on inrush current level. Also, make sure there is very less capacitance before the Hot-swap device as the device does not have control on the cap placed before it. I suggest to remove BC461 .

Best Regards,
Rakesh

0 Jeff Hsu over 6 years ago in reply to Rakesh

Prodigy 90 points

Hi Rakesh,

Thanks, looks like removed BC461 can fix this issue, so now we closed this item.

Regards
Jeff

0 Rakesh over 6 years ago in reply to Jeff Hsu

TI__Guru** 105361 points

Hi Jeff,

Good to hear that helped.
Can you close this thread.

Best Regards,
Rakesh

0 Jeff Hsu over 6 years ago in reply to Rakesh

Prodigy 90 points

Hi Rakesh,

Thanks and sorry, I don't know how to close this, can you let me know?

Regards
Jeff

0 Rakesh over 6 years ago in reply to Jeff Hsu

TI__Guru** 105361 points

Please click "This resolved my issue" button. The thread gets closed automatically.

0 Jeff Hsu over 6 years ago in reply to Rakesh

Prodigy 90 points

Hi Rakesh,

Thanks, but I am no found any "This resolved my issue" button on this WEB page, so please advise more.

Regards
Jeff 12/14

0 Rakesh over 6 years ago in reply to Jeff Hsu

TI__Guru** 105361 points

Hi Jeff,

No issue. leave it. Have a nice weekend.

Best Regards,
Rakesh

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LM5069: LM5069 My issue is power adapters can spark when plugged in due to inrush current