Q: TPA3110D2 frequency response

Hi team,
 
My customer designs home theatre solutions. They are developing a 5.1 system based on TPA3110D2. On their board they see that gain rolls of at higher frequency -- around 2dB less beyond 10KHz (for resistive load as well as for 8R speakers). This tallies well with datasheet figure 16 on page 10. They would like to have the frequency response flat upto 20KHz. They are using external LC filters and gain of 36dB (both GAIN pins to HIGH). I had asked them to repeat the observation with half-power output (instead of full power), but the observation is same.
 
Let me know if flat frequency response upto 20KHz can be achieved by changing any external components or is this IC limitation ? Customer is doing system level testing right now, so urgent feedback is highly appreciated.
 

Q: Re: TPA3110D2 frequency response 

Hi,

The freq response should be flat -- the reason fig 16 slopes off is due to the complex load impedance -- we have 8 ohms in series with 66 uH which means there is a frequency component in the load with frequency. Also, the AUX-0025 introduces some loss in gain at high freq due to its -3 dB point.

So, in order to accurately measure gain versus freq, you need a constant load (a non-inductive power resistor), and an output LPF (LC) with a -3 dB point way out from 20 kHz in order to not have the filter affect the measurement.