LM5010 Trouble

Handy Chandra

Other Parts Discussed in Thread: LM5010

Hi,

I am using LM5010 to convert 48 to 24V 1A and 48 to 12V 1A. As I am a beginner in SMPS, i use ti webench. However, I have three problems :

- Under no load condition, i could hear noise from the PCB. Is this normal ?

- When i draw 500 mA from both topology, The noise stop. But LM5010 got very hot but still operating. Is my thermal design wrong ? i am using 4 layer PCB

- When still drawing 500 mA current, after it got hot enough, i could hear noise from the PCB again.

Anyone know whats wrong with my design ? I have attached the webench document here

webench.pdf

over 9 years ago

0 Vijay86929 over 9 years ago

TI__Genius 11490 points

Hi Handy,

You must have used a circuit schematic program to create your circuit. That will be a better circuit to review for potential errors.

0 Vijay86929 over 9 years ago in reply to Vijay86929

TI__Genius 11490 points

In the webench document, Rsereis is 1m(ohm). This is typ in the 100m to 1 ohm range. Perhaps you can try increasing this resistor to see if it stabilizes the circuit.

0 Handy Chandra over 9 years ago in reply to Vijay86929

Prodigy 40 points

I have tried to increase the resistor value to 100mohm, but the same problem still occurs. Any other idea ?

0 JohnTucker over 9 years ago in reply to Handy Chandra

TI__Guru**** 191445 points

Can you post your PCB layout?

0 Vijay86929 over 9 years ago in reply to Handy Chandra

TI__Genius 11490 points

Hi Handy,

I suggest increasing the resistor further just to confirm if it is ripple induced or because of something else.

Thanks and regards,

0 Handy Chandra over 9 years ago in reply to JohnTucker

Prodigy 40 points

Here i attached the top layer and power plane. I am using split power plane.

Here is the layer configuration of the PCB :

layer 1 : signal

layer 2: ground

layer 3 : power

layer 4 : signal

images.zip

0 Handy Chandra over 9 years ago in reply to Handy Chandra

Prodigy 40 points

I found out the cause of noise problem : It seems that i added a diode and then a 100uF electrolytic cap on the output of LM5010. The capacitor causes switching frequency of LM5010 drops to audible frequency.

Power management

Power management forum

LM5010 Trouble