Will PCB layout impact the SNR and THD for TPA3110D2?

Hi, CG,

Your SNR seems to be quite low, and it could definitely be due to schematic, PCB layout, components, etc.

-d2

Hi Don,

    We just found it is because the inductor diference, if we swap the inductors, the SNR value will change. But all the inductors are the same type 15uH (TDK: VLC6045T-150M) as recommended in TPA3110D2 Spec  Page 24 for 4 OHM load. Should we use larger value inductor like 22uH?  The inductor spec is attached. Thanks a lot.3666.TDK-VLC系列电感.pdf

Today we tried another LC filter  22uH+0.68uF (X7R),there is no obvious change for SNR.  We wonder what kind of  LC  components should be used for TPA3110D2 with 4 OHM load.   

Hi, CG,

We have an app note that discusses LC filter design. You can find it here.

-d2

Thanks Don. 

By the way, I use a Millivoltmeter to measure SNR.  Will the result  be different between using an Audio Analyzer and a millivoltmeter?  Or should I add a RC LPF before the millivoltmeter?

Hi, CG,

I'm not sure about the meter. If you look at the output waveform on a scope, you will see significant ripple at 250 kHz (the switching frequency), which is probably above the frequency that your meter can resolve. I am not sure what it will do with that data.

-d2

Hi Don,  

 You are right. Please refer to the pic below. There is peak at 300KHz and 900KHz.

But I wonder why there is still left so much switching noise while I have already used a LC filter. It should be  very little. 

.

Hi, CG,

Sorry for the delay. Your waveform looks very strange. If you measure it differentially (ch1-ch2) it is usually much easier to see the actual waveform that way.

-d2

I've measured (ch+) -(ch-),  there is still an obvious amplitude difference (about 80mV) .

And if I add an RC (100 OHM+56nF) filter before the scope probe, the 300KHz noise will be very little. The SNR will be good.

Ch +:

Ch -:

Thanks a lot.