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TLV320AIC3104-Q1: External amplifier for differential outputs from the RIGHT LOP/M signals

Pradeep Mohan
Intellectual 725 points
Part Number: TLV320AIC3104-Q1
Other Parts Discussed in Thread: TLV320AIC3104, TAS5411-Q1

Hello,

we are using the TLV320AIC3104 with a Quectel EC21 modem to enable voice calls. Our previous prototype worked fine when we used single ended outputs, but now we switched to the RIGHT_LOP/M outputs.

1. Since we do not want to have the amplifier on the PCB, we were wondering if there are any options you could recommend for external audio amplifiers.

2. The more important question : What happens if I connect an external amplifier that accepts only single ended inputs? Can I connect RIGHT LOP to the + and RIGHT LOM to the - ? Would it just be a reduction in gain? I just tried this and I can barely hear anything. 

3. Quectel recommends the following circuit if I want to use an audio jack (for testing) with the differential signals. SPK_P is RIGHT_LOP. Would this work? RIGHT_LOP is not a high power driver and I was wondering if the following circuit would work at all.

Thank You.

 

  • 0
    TI__Mastermind 30210 points

    hello Pradeep,

    1:  what are your amplifier requirements?   The TAS5411-Q1 is a great option.  here is a comparison that one of our Applications engineers made for an ecall reference design

    2: This is not a recommended configuration.  This is possible, but at a performance cost.  Ideally, you would use an opamp to convert from differential to Single ended, but we realize this often adds cost to a system.  The other option would be to place an equivalent Load on the unused Differential ouptut, but again this comes at the cost of lower performance.  

    3: can you explain that a little more?  your picture doesn't seem to match your words.  I don't see Right_LOP? 

    what I can say is that RIGHT_LOP, and Left_LOP will not be able to drive low impedance headphones.  These outputs have a minimum load impedance of 10k.  The HPOUTS  have a minimum load impedance of 16R.   

  • 0 in reply to Steve-Wilson
    Intellectual 725 points

    Hello Steve,

    Thank you for your prompt response.

    1. I love the TAS5411-Q1 for our requirements. I also found the same on the eCall reference design from Quectel. However the requirements stipulate an external amplifier, preferably a ready to buy aftermarket solution instead of an on board solution.

    2.  Thank you for the info. I think we will go ahead with the single ended configuration using the capacitor and resistor values recommended by you here .

    3. I apologize for the vague schematic. To clarify, RIGHT LOP is SPK_P and the MIC_P and MIC_N are the differential inputs MIC1RP/RM. Please find in the attached schematic below the labels SPK_P, MIC_P and MIC_N

    If the differential outputs cannot drive the low impedance headphones, then I assume there must be an error in Quectel's recommended design.

    Thanks again for the support.

  • 0 in reply to Pradeep Mohan
    TI__Mastermind 30210 points
    You're welcome Pradeep,

    re:2 - yes, the HPR/LOUTS can be set to SE mode, That would be ideal for a single ended output.

    re:3 - right, as I mentioned the HPR/LOUTS are able to drive headphones.

    best regards,
    -Steve Wilson