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TPA3001D1 Input questions

Don Dapkus
Guru**** 189399 points
Other Parts Discussed in Thread: TPA3001D1, OPA2134, TPA3112D1, TAS5727, TPA3004D2

A customer asks:

I am using TPA3001D1 to drive a 20W speaker. The audio signal to this chip is on INP ac coupled with a 0.47 uF capacitor. INN is tied to ground.

My question is the audio signal amplitude can swing up to  +/- 5 volt do I have to rectify the negative part of the signal or is it OK for the chip? 

To increase or decrease the volume can I use an electronics pot to increase or decrease the amplitude at the input?

The audio source is fed via OPA2134.

 

 

  • 0
    TI__Guru**** 189399 points

    Hi,

    The TPA3001D1 is a pretty old part, we have cheaper, better performing parts now if this is for a new design. Look at TPA3112D1 for example.

    INN should be tied to ground thru the same value capacitor as INP to reduce turn-on pop when using a single-ended source.

    The input blocking cap takes care of level shifting the DC offset on the audio signal. it sounds like you need to attenuate your input signal slightly as the maximum input signal we can accept is 7V.

    You could use some kind of potentiometer to control the volume. We have TPA3004D2 which has the pot built-in, and we have TAS5727 which has a digital volume control, but it only accepts I2S digital audio input. If your source is analog, then you probably can't use the TAS5727.

    -d2

  • 0 in reply to Don Dapkus
    Prodigy 30 points

    I will change the part in production to the part you mentioned. However, we wanted to experiment with a switching power supply. This was not a good idea since the speaker would hum, we were able to put a 0.47 uF cap. between audio ground and chassis ground and lowered the hum intensity (loudness). We went back to a linear power supply.

    Do you have a suggestion for that or are we doing something wrong?

  • 0 in reply to kaveh dadkhah
    TI__Guru**** 189399 points

    Hi, Kaveh,

    Nearly every one of our class-D amps is powered by an SMPS. The most common problem I see is ground loops. The fact that you improved it by adding some capacitance proves that. Try playing around with the grounds a little more, and you should be able to completely eliminate the hum.

    -d2