LM5050-1 Output unstableness

Masazumi Ishii

Genius 3945 points

Other Parts Discussed in Thread: LM5050-1, LM5050-2

Hello.

LM5050-1 is being used.

There is a question.

Vbus=48V

Increase the capacity load of the capacitor of 48VBUS.
The output at this time, a phenomenon that oscillates occurred.
In addition, it will become unstable gate voltage of the FET.

Please tell me cause and countermeasures.

Thank you.

over 8 years ago

0 Aramis P. Alvarez over 8 years ago

TI__Genius 10370 points

Hi Masazumi,

Here's a great app note that explains exactly what you're talking about and how to fix it: http://www.ti.com/lit/an/slva684/slva684.pdf

In the app note, it states to increase the input cap 10x more than the output cap. Another solution is to install an RC filter on the sense lines (look below):

I hope this helps.

Best Regards,

Aramis P. Alvarez

0 Masazumi Ishii over 8 years ago in reply to Aramis P. Alvarez

Genius 3945 points

Hello.

Thank you for your answer.

There are two points ask further questions.

1 for Another solution is to install an RC filter on the sense lines (look below)

C1 (capacitor), R1 (resistance), or you may If you put the things of any value ?

2 When Vin = 0V Vs = 0V, applied to the input pin (off) = 5V
Is this state, the IC is not damaged ?

thank you.

0 Aramis P. Alvarez over 8 years ago in reply to Masazumi Ishii

TI__Genius 10370 points

Hi Masazumi,

A value of 0.1uF for C1 and 10ohm for R1 should work. To answer your 2nd question, the IC won't be damaged. You can put Vin = Vs = 0V and Off=5V and the IC will be fine :-)

Best Regards,

Aramis P. Alvarez

0 Masazumi Ishii over 8 years ago in reply to Aramis P. Alvarez

Genius 3945 points

Hello.

I have a question.
A value of 0.1uF for C1 and 10ohm for R1 should work.
A was the answer,

In this case, is it understandable that understanding can be dealt with independently of input and load capacitors?
Does the same result also be obtained when doing with LM5050-2?
Or will you not need resistors and capacitors for R1 and C1?

thank you.

0 Aramis P. Alvarez over 8 years ago in reply to Masazumi Ishii

TI__Genius 10370 points

Hi Masazumi,

If you have the same oscillations with the LM5050-2, you can add the same circuit described above for the LM5050-1.

Best Regards,
Aramis P. Alvarez

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LM5050-1 Output unstableness