LM3481-Q1: Output ripple is present in the reference design generated in webench

Swathin ES

Part Number: LM3481-Q1
Other Parts Discussed in Thread: LM3481,

hi,

I was working on a aux power supply for an automotive application, so I decided to generate a boost PS solution with LM3481 Q1 with webench. My input is a varying DC source from 9VDC to 16VDC and output is fixed 20VDC with a current of 0.5A total power is 10W and operating frequency is 200kHz.the design suggested from webench having a lot of ripple present at the output which is even available in their simulation tool it self. Can anyone help me with this matter? With low ESR distributed capacitors, I have been able to reduce the ripple to 7mVpp; however, the ripple frequency and shape remain the same.

over 2 years ago

0 Brigitte over 2 years ago

TI__Guru 65170 points

Hello Swathin,

7mV pp seems to be a low ripple, so I think this is ok. Ripple on the output of a boost converter is always present.

Did you select low cost when creating the design in Webench?

Best regards,
Brigitte

0 Swathin ES over 2 years ago

Prodigy 130 points

I selected the balenced design. Ripple in the output fromwebench was beyond the limits as you can see in the image. With some modifications I did able to reduse it. But my problem is now the frequency of ripple is exactly same as the switching

0 Shaheen Makandar over 2 years ago in reply to Swathin ES

TI__Expert 3090 points

Hi Swathi and Brigitte,

We will check the above reported issue wrt LM3481 Q1 and get back to you once we have an update on this.

Regards

Shaheen S M

0 Praveen Badiger over 2 years ago in reply to Shaheen Makandar

TI__Expert 8365 points

Hi Swathi and Brigitte,

We have resolved the issue. The changes will be available on ti.com by mid of next week.

Thanks & Regards,

Praveen

0 Swathin ES over 2 years ago in reply to Praveen Badiger

Prodigy 130 points

Hi Praveen,

Since our design timeline is spilling, may i know what kind of changes you have done to the design.

Thanks and regards

-Swathin

0 Praveen Badiger over 2 years ago in reply to Swathin ES

TI__Expert 8365 points

HI Swathin,

There was issue with diode model. We have updated the diode parameters. This helped to reduce the spikes in output voltage. Meanwhile , Please simulate the Pspice transient mode available in the product folder.

https://www.ti.com/lit/zip/snvm713

Thanks & Regards,

Praveen

0 Swathin ES over 2 years ago in reply to Praveen Badiger

Prodigy 130 points

Hi praveen,

thanks, is this IC model is updated one?. but issue was with the diode model right?

Thanks

Swathin

0 Praveen Badiger over 2 years ago in reply to Swathin ES

TI__Expert 8365 points

HI Swathin,

IC model is fine. There was issue with external diode as highlighted below.

Thanks &Regards,

Praveen

0 Swathin ES over 2 years ago in reply to Praveen Badiger

Prodigy 130 points

Hi Praveen,

I tried alternate diode models as well, the result is same.

Thanks and regards

Swathin

0 Praveen Badiger over 2 years ago in reply to Swathin ES

TI__Expert 8365 points

HI Swathin,

Currently there is an issue with all diode models. Changes will be reflected by next week. Kindly share the WEBENCH design link you are looking for. I will share the updated simulation results.

Also , Meanwhile you can use TINA_TI or Pspice model for simulation as given below.

https://www.ti.com/product/LM3481#design-tools-simulation

Thanks &Regards,

Praveen

0 Swathin ES over 2 years ago in reply to Praveen Badiger

Prodigy 130 points

Hi Praveen thanks for the response,

the export simulation option for the particular design is not there, only pdf export available .i can share the requirement

Input :9-16VDC

Output :24V, 16W

Frequency :200khz

IC:LM3481 Q1

This for automotive application( Onboard battery charger aux supply)

i used the p spice unencrypted model in LT spice and checked, amplitude of ripple got reduced but with the suggested components the ripple level is still high.

Thanks and regards

Swathin

0 Praveen Badiger over 2 years ago in reply to Swathin ES

TI__Expert 8365 points

HI Swathin,

Below is the design report. Please find the simulation waveform at page no.10

./cfs-file/__key/communityserver-discussions-components-files/196/WBDesign15203.pdf

You can also share the WEBENCH design using 'Share Design' option.

Thanks &Regards,

Praveen

0 Swathin ES over 2 years ago in reply to Praveen Badiger

Prodigy 130 points

Thanks Praveen,

But my requirement was for 16W ie 0.6666A output. this is 2A(48W).

0 Praveen Badiger over 2 years ago in reply to Swathin ES

TI__Expert 8365 points

Hi Swathin,

Sorry for the wrong Iout. I have simulated the design with Iout=0.66A.Below is the webench design report attached.

/cfs-file/__key/communityserver-discussions-components-files/196/WBDesign15205.pdf

Thanks &Regards,

Praveen

0 Swathin ES over 2 years ago in reply to Praveen Badiger

Prodigy 130 points

Hi praveen,

thanks or the design. Is this updated on webench ?. And the shared document is with LM3481 not LM3481 Q1.

-Swathin

0 Praveen Badiger over 2 years ago in reply to Swathin ES

TI__Expert 8365 points

Hi Swathin,

The fix is available on ti.com. However, electrical simulations are failing for all devices due to infrastructure issue. We are working on it. Please note that, LM3481 and LM3481-Q1 uses a same model file. Simulation results would be same on WEBENCH.

Thanks & Regards,
Praveen

0 Praveen Badiger over 2 years ago in reply to Praveen Badiger

TI__Expert 8365 points

Hi Swathin,

LM3481-Q1 electrical simulation is working fine on ti.com.

Thanks & Regards,
Praveen

0 Swathin ES over 2 years ago in reply to Praveen Badiger

Prodigy 130 points

Hi Praveen,

Thanks for the update, i have checked. still i could see a ripple of around 120mvpp. is there any way to get the design simulation file for detailed analysis.

-Swathin

0 Praveen Badiger over 2 years ago in reply to Swathin ES

TI__Expert 8365 points

Hi Swathin,

Below is the unencrypted model file which is available on product folder.

https://www.ti.com/lit/zip/snvm713

Thanks & Regards,
Praveen

0 Swathin ES over 2 years ago in reply to Praveen Badiger

Prodigy 130 points

Hi Praveen,

is there any way to get the whole design file

-Swathin

+1 Praveen Badiger over 2 years ago in reply to Swathin ES

TI__Expert 8365 points

Hi Swathin,

We have only model files and documents which are already available on product folder. We don't have design files.

Thanks & Regards,
Praveen

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LM3481-Q1: Output ripple is present in the reference design generated in webench