TPA3250: problem of LC filter

dong chen

Prodigy 190 points

Part Number: TPA3250
Other Parts Discussed in Thread: , DXP

Dear all

I has used TPA3250 for PBTL Application. I designed evaluation board follow TPA3250D2EVM.

Component on board is follow all TPA3250D2EVM's BOM.

The schematic diagram and PCB is as follows.

TPA3250 's output have a high voltage ripple,nearly 1V. The voltage ripple followed TPA3250 's switch frequency.If I change the frequency resistance the voltage ripple is followed.

It seems LV filter is not effect. I don't know what about TPA3250D2EVM 's effect in this part.

How can I fixed it?

Thank you.

HD-1024-PA-A-00.PDF

over 6 years ago

0 Shawn Zheng over 6 years ago

TI__Mastermind 24835 points

Hello, we are looking into this and Justin will get back to you later.

0 dong chen over 6 years ago in reply to Shawn Zheng

Prodigy 190 points

Thanks,PCB Layout is in rar package . It 's designd by Altium DXP.

Because of the size , I can only design this.

HD-1024-PA-A-00.zip

0 Justin Bohr over 6 years ago in reply to dong chen

TI__Mastermind 27850 points

This is actually the filter doing exactly what it should. With the TPA3250, the PVDD supply is 36V. In BTL operation this will result in a total voltage difference across the load of nearly 72V. Now looking at the resulting ripple on the output of 1V, and taking the max voltage across the load, 72V you can calculate the attenuation. Attenuation = 20*log(1/72) = -37.14 dB. Now if you take a look at our Class-D LC Filter Designer, and configure it to the EVM's specification (common mode, 10 uH, 1uF, 4R load) you will see at around 450 kHz, the attenuation is near -37 dB.

If your application is audio then you should not be worried about this frequency, unless you are worried about EMI for a certification. If you are failing a certification due to this, you will need to add another filter such as a snubber or a choke on the output.

Justin

0 dong chen over 6 years ago in reply to Justin Bohr

Prodigy 190 points

Dear Justin

Thank you for your help!

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TPA3250: problem of LC filter