TPS65145: ripples with frequency around 5kHz

Hi Hanno,

Seems you didn't paste the link successfully, could you please retry? And it will be helpful if you can also share the waveforms.

BR

Patrick

Hi Patrick,

I am sharing the waveforms for your reference. 

BR

Rohan Munjal

Hi Rohan,

Are the yellow and green waveforms both the boost output voltage with AC and DC coupling?

BR

Patrick

Hi Patrick,

Yes, Green is with AC coupling and Yellow is with DC coupling. 

BR

Rohan

Hi Rohan,

Will increase the output capacitance help to improve?

BR

Patrick

Hello Patrick,

I think increase in the ouput capacitance won't help so much. I have tried putting a load on the output of boost converter. Basically i used different resistor sizes (with appropriate power rating) as a load. I observed that after a certain amount of load, noise starts to reduce. I do not have waveform of it. You can test it once. In our design (which is basically a design of TI), we have a limited load only. I am attaching a PDF file for your reference, which contains the reference design of TI. May be you can use the TI's evaluation kit for testing.

 dlplcr65evm.pdf

Hi Rohan,

Could you please capture the waveform of TPS65145 SW node? The ripple is likely caused by the light load mode.

BR

Patrick

Hi Patrick,

I am attaching the captured waveform at SW node. Yellow waveform is with DC coupling, green waveform is with AC coupling. 

Hi Rohan,

What is your acceptable ripple? I will see if it can be improved.

BR

Patrick

Hi Patrick,

The acceptable range of ripple is less important than the audible noise associated with it. There is a buzzing sound that comes continuously. We need to eliminate this audible noise. 

BR 

Rohan

Hi Rohan,

Understood, and do you also have the waveform of inductor current? Firstly we need to confirm whether this noise is from inductor or the output capacitors.

BR

Patrick

Hi Patrick,

Unfortunately, i do not have the waveform of inductor current and i cannot measure it. 

BR

Rohan

Hi Rohan,

So could you please roughly check where is the noise from? Inductor or output capacitor?

BR

Patrick

Hi Patrick, 

One end of Inductor is connected to SW pin, i have already provided the waveform for it. Secondly, the output capacitor waveform is the one with ripples, which i initially posted. Please use the evaluation board of TI to understand the problem. 

With Regards

Rohan 

Hi Rohan,

Unfortunately I don't have the reference design board, but I can try to reproduce this ripple issue on TPS65145EVM.

BR

Patrick

Hi Patrick,

That would be great. Will wait for your feedback. 

Hi Rohan,

Please let me know if you have new findings meanwhile, thanks.

BR

Patrick