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LM4864: Audio Amplifier Indication with Toradex Colibri SOM

Daniel Luis Martins
Prodigy 230 points

Part Number: LM4864
Other Parts Discussed in Thread: TPA0211, TPA0213, TPA6203A1, TPA6211A1

Dear Sirs,

We have developed electronic equipment for the agricultural sector. Now we are finalizing the development of a HMI device, similar to a tablet. But, more robust and for agricultural applications.

As processor, we are using a Toradex SOM, line Colibri iMX6. I need in this project an output for a Speaker. I do not need high sound quality. I just need a volume that is enough to be heard inside operating cabins.

I need a speaker to play only alerts / warnings. I need to developed one hardware using the module's headphone output (or another audio output). After that, I needed one amplifier to play a Speaker.

Is it possible to indicate some PN for this application?

For testing, I developed a PCI with the LM4864 amplifier on the Headphone output of the module. For Speaker, I used one 8Ohms / 0.5W CUI Speaker.

However, the sound output on the Speaker is very, very low even at maximum volume.

To help, I've attached the schematic I used for the LM4864.

Actually I'm not sure if I did something wrong with the LM4864, or if the output power to my application should be higher - and how much?

Kindly,

Daniel MartinsSchematic LM4864.pdf

  • 0
    Prodigy 230 points
    Complementing the information. The Colibri Headphone_L analog output comes from the SGTL5000 CODEC, probably from the LINEOUT_L output.
  • 0
    TI__Mastermind 20085 points
    Hi Daniel,

    I have reviewed the schematic and it seems to be right. But the layout has something wrong you are connecting IN- pin to the shutdown circuit(transistor) and EN (Shutdown pin) to the input resistors (Ri and Rf). I think that this is causing your issue.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer
  • 0 in reply to José Luis
    Prodigy 230 points

    Hi Jose,

    Thanks for your reply and attention.

    One thing about the layout photo, LM4864 is on the bottom of my PCI.

    So, the image its mirror.

    Then, the connection are OK.

    Kindly,

  • 0 in reply to Daniel Luis Martins
    TI__Mastermind 20085 points
    Hi Daniel,

    The schematic and layout seem to be right.
    You can have a look at the following devices: TPA0213 and TPA0211, they are mono class-AB audio amplifiers with stereo headphones and they are able to deliver higher output power than LM4864. I think that they fit much better in your application.
    On the other hand, you can have a look at the following devices: TPA6203A1 and TPA6211A1, they are mono fully differential class-AB audio amplifiers and they are also able to deliver higher output power than LM4864.
    I hope this helps you.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer