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TLV320AIC3254: Single-ended input Vs Differential input

Dileep Raghu
Prodigy 230 points
Part Number: TLV320AIC3254


Hi,

I have used TLV320AIC3254 codec earlier with Single-ended input to IN1L (GND reference) & IN1R (audio signal), this was working fine. Now for IN1L & IN1R I have given diffrential input and output audio is just a loud noise, no proper audio is audible. Is there any code settings or hardware changes for single-ended input and differential input.

Regards,
Dileep

  • 0
    TI__Guru 57800 points

    Hi, Dileep,

    The effective analog PGA gain of the 'AIC3254 changes when the codec is configured in differential mode, basically it is increased by 6dB under the same input resistor conditions. User should adjust either the gain in he PGA or the input resistor value to adjust the total gain for the required setting, please refer to section 2.3.2.1 of the 'AIC3254 Applications Reference Gain.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Prodigy 230 points

    Hi Diego,

    If I use bypass path (IN1 to HP) to test differential audio input, can I get proper audio out on HPL & HPR.

    Apart from input register conditions, is there any register settings we have to do in codec to configure in differential mode.

    Thanks and Regards,

    Dileep 

  • 0 in reply to Dileep Raghu
    TI__Guru 57800 points

    Hi, Dileep,

    As the headphone drivers are not differential, If you bypass the audio signal to the HP output, only one leg of the differential pair will be sent to the headphone output. 

    The only required setting to configure the codec in differential mode is the input routing.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Prodigy 230 points
    Hi Diego,

    Can you help me out by showing routing path on block diagram for both single-ended and differential pair inputs.

    1. Single-ended:
    IN1_L - GND referenece
    IN1_R - audio signal

    2. Differential signal given to IN1_L & IN1_R.

    I want outputs on HPL, HPR, LOL, LOR and also record the audio.
    HPL & HPR output going to a Headset.
    LOL & LOR output going to a speaker.

    Thanks and Regards,
    Dileep
  • 0 in reply to Dileep Raghu
    TI__Guru 57800 points

    Hi, Dileep,

    Can you please clarify about the output routing?, In order to pass the input differential signal to the outputs, you need to use the Mixer amplifier (MAL/MAR) and route the corresponding output to either HP and LO outputs. Do you want to capture a mono differential signal and send it to all the outputs and ADC or you are expecting to have a differential output signal in HPL/R and LOL/R?.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Prodigy 230 points

    Hi Diego,

    I am attaching the routing path shared by you, will it work for differential inputs. I am expecting differential inputs at IN1_L & IN1_R to be routed as differential output signal in HPL/R and LOL/R and record as well.

    Thanks and Regards,

    Dileep

  • 0 in reply to Dileep Raghu
    TI__Guru 57800 points

    Hi, Dileep,

    The differential input should work the same way as a single-ended input in terms of the input routing, as you can see, the differential input is taken into the PGA and then it is streamed in a single channel source that can be routed to the outputs as described previously or to the recording path. My question was about the output signal configuration. Assuming you have the described input in differential mode and you want to send this signal to the ADC for record and stream the output in a differential mode through HP and LO, the block diagram would be as follows (from the Applications Reference Guide):

    Please let me know if you have any question about it.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer