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LM49250: Left and Right channel connections

Alwyn DSouza
Intellectual 360 points
Part Number: LM49250

In the LM49250 datasheet I see the following connections show in single ended configuration for the left and right line inputs.

As shown above the one stereo channel is connected to L1/L2 and another stereo channel is connected to R1/R2

Shouldn't the channels be connected like

Stereo Channel 1 to be connected to L1 / R1.

Stereo Channel 2 to be connected to L2 / R2.

The second question is:

If I'm not using the loudspeaker do I need to connect the Vdd (LS) supply.?

TIA

  • 0
    TI__Guru** 102405 points

    Hi TIA,

    According to Table 4, L1 and L2 are mixed together and the same applies for R1 and R2. This is the way the internal mixer works so this has to be followed externally by hardware.

    Regarding VDD(LS), the device description suggests that speaker drivers are powered by VDD(LS) while headphone drivers are powered from internal LDO, which is powered by VDD as suggested in the block diagram.
    Based on this, it should be possible to leave VDD(LS) disconnected if speaker driver is not used. However I would suggest to test and verify this; unfortunately we don't have evaluation modules for most of these old-legacy devices, and it applies for this one.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators

  • 0 in reply to Ivan Salazar
    Intellectual 360 points

    Ivan Salazar said:
    According to Table 4, L1 and L2 are mixed together and the same applies for R1 and R2. This is the way the internal mixer works so this has to be followed externally by hardware.

    I was asking this because the diagram implies that a Stereo channel has to be connected to L1/L2 which is wrong since a stereo channel contains a left and a right channel, so it should have been connected to L1/R1 and another stereo channel should have been connected to L2/R2.

    Please confirm if my thinking is correct, furthermore since you have verified that L1/L2 channels are being mixed internally, I believe the connection I described should be the way to go.

    Ivan Salazar said:
    However I would suggest to test and verify this; unfortunately we don't have evaluation modules for most of these old-legacy devices, and it applies for this one.

     

    I have checked several of TI's modern devices but they contained I2S/ADC/DAC internally and were way overkill for this application, If you have any other recommendation for a modern device that contains the required blocks of mixer, 2 stereo + 1 mono input and a heaphone driver please let  me know.

    BTW is TI thinking of EOL 'ing this device any time soon?

    TIA

  • 0 in reply to Alwyn DSouza
    TI__Guru** 102405 points

    TIA,

    I understand now what your question is about the inputs, you can do any of the two options basically:

    • Mix each stereo pair by L1/L2 and R1/R2
    • Mix each side of stereo pairs separately by L1/R1 and L2/R2

    The mixer is the same, you can use the hardware inputs as you need.

    There is no information about EOL for this device. Perhaps a two chip solution can fit in your application.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators