• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 30 subscribers
  • Views 3314 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

I2S audio decoder and mixer solution

uMin
Intellectual 860 points
Other Parts Discussed in Thread: LM49350, LM4675

Hi,

My customer is looking for an audio solution as follow:

  • To decode and mix two I2S audio sources together.
  • The resulting audio will go through a Class-D amplifier to drive two speakers
  • To monitor ambient noise and control the output volume according to the ambient noise.

May I know whether or not LM49350 is able to perform all the above functions ?

Otherwise, any suggestions to the above requirement ?

 

Thanks and Best Regards,

CM.

 

  • 0
    TI__Genius 13650 points

    Hi CM,

    • To decode and mix two I2S audio sources together.

    Yes, the LM49350 is able to do this. It also contains a sample rate converter, so that it is possible to operate the two I2S sources at different sample rates if desired.

    • The resulting audio will go through a Class-D amplifier to drive two speakers

    Only one of the amplifiers is a class D amplifier, capable of driving an 8 Ohm loudspeaker at 1.2W. It is possible to use the device in stereo loudspeaker mode by connecting an external loudspeaker amplifier LM4675 to the differential AUX output of the LM49350 (see example in fig. 3 in the datasheet). What are the output power requirements for the system? 

    • To monitor ambient noise and control the output volume according to the ambient noise.

    The LM49350 contains an ALC on the ADC with a level detect. By reading back the value from the level detect function at regular intervals, the controller can determine the level of ambient noise and adjust the output volume accordingly. Is this mechanism acceptable, or is it necessary for the codec to perform the ambient noise compensation without input from the controller?

  • 0 in reply to Ben Kasemsadeh
    Intellectual 860 points

    Hi Ben,

     

    Thanks for your fast response.

    The required output power is ~3-4W per channel.  So they probably need another Class-D amp to do this ?

     

    • The LM49350 contains an ALC on the ADC with a level detect. By reading back the value from the level detect function at regular intervals, the controller can determine the level of ambient noise and adjust the output volume accordingly. Is this mechanism acceptable, or is it necessary for the codec to perform the ambient noise compensation without input from the controller?

    The preference is to perform the ambient noise compensation without the controller involved.  Is there another part which can do this by itself ?

     

    Thanks,

    CM.

  • 0 in reply to uMin
    TI__Genius 13650 points

    Hi CM,

    yes, we have several parts with a miniDSP which perform the Environmental Noise Compensation algorithm. This algorithm will perform the function you describe without involvement from the controller. 

    The AIC3262 has a miniDSP and integrated stereo Class D outputs, but since it supports only 8 ohm speakers (1.4W/ch @ 5V supply), I assume the output power will be too low for  your customer.

    I recommend using a miniDSP codec without integrated speaker amp such as AIC3254 or an AIC3256, and connect the appropriate class D amps to it. A wide range of stand-alone amps is available, for example TPA2010, TPA2011, or LM4675 (mono, 4 ohm), TPA2012 (stereo, 4 ohm), TPA2013 (mono, 4 ohm boosted). TPA2015 (mono, 8 ohm boosted),  

    Would AIC3254/56 suit the customer needs in terms of other I/O requirements?

    What loudspeaker impedance and loudspeaker supply voltage is intended?