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LM48901

Michael Sprauve
Prodigy 20 points
Other Parts Discussed in Thread: TPA3100D2, TPA3110D2

Hi,

A couple of questions in regards to this chip

1)How do you connect more than 4 speakers to the device (we are looking at 6 speakers)

2)Can we use the output to drive a higher power amp section

  • 0
    TI__Prodigy 185 points

    1)How do you connect more than 4 speakers to the device (we are looking at 6 speakers)

    You use 2 LM48901s.to achieve 5-8 speaker outputs.  Each LM48901 has 4ch output - more channels requires additional devices.  We support up to 4 LM48901s resulting in 16 speaker channel output.

      For details about connections/programming please refer to the datasheet pages 43-44. http://www.ti.com/lit/ds/symlink/lm48901.pdf

     

    2)Can we use the output to drive a higher power amp section

    There are 2 ways to do this.

    1. Filter the class D output back to an analog signal.  Then use analog input Class Ds of your output power requirements.  We can reccomend a TI class D if you share your requirements.

    2. Utilize the analog input of the LM48901.  Then you can use the digital output (I2S) to go to external I2S input Class Ds  We can reccomend a TI class D for this as well.

  • 0 in reply to Eric Eklund
    Prodigy 20 points

    Thanks for the reply...In regards to Question #1 thanks for pointing out that page in the spec sheet. In regards to Question #2, we plan on using both the Analog inputs along with the I2S inputs so it seems the only option is Option #1 - filter the class D outputs back to an analog signal. Our power requirements are

    Driver Freq Range Power
    Size
    Woofer 4-4.5" 42-300 20-25 x2
    Mid 4-4.5" 42-3K 20-25 x2
    Tweeter 3/4-1" 3K-22K 20 x2

    We are also considering combining the Mid and Woofer to operate below 300 Hz. Also any suggestions on filtering out the Class D outputs would be very helpful

  • 0 in reply to Michael Sprauve
    TI__Guru**** 189399 points

    Hi, Michael,

    Take a look at TPA3110D2... It's a little below your power points, but CHEAP. Next up is TPA3100D2 which can do 20Wx2, but a lot more expensive.

    As for the filtering, I'm not an expert on the LM part, but I'd assume if you used a resistor in series with each input, with a cap across them (on the chip side) forming a first order LPF you'd be set.

    -d2

  • 0 in reply to Don Dapkus
    TI__Expert 3350 points

    Michael,

    I would recommend a passive RLC low pass filter.  Select a resistor value ~200-300ohms so you don't load down the 48901, but still allowing you to use reasonable inductor values to achive a desired -3dB rolloff around 60-90kHz.  If noise is an issue, you may have to go to a higher order filter, or add an active filter circuit after the RLC.

     

    royce

  • 0 in reply to Eric Eklund
    Expert 1530 points

    Eric Eklund said:

    1)How do you connect more than 4 speakers to the device (we are looking at 6 speakers)

    You use 2 LM48901s.to achieve 5-8 speaker outputs.  Each LM48901 has 4ch output - more channels requires additional devices.  We support up to 4 LM48901s resulting in 16 speaker channel output.

      For details about connections/programming please refer to the datasheet pages 43-44. http://www.ti.com/lit/ds/symlink/lm48901.pdf

     

    If we need six channels is it possible to use an LM48901 with LM48903? Or do I need to use 2x LM48901 as described above.

    Thanks