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Original question:

TPA6304-Q1: GAIN related issue

TPA6304-Q1: circuit check

Huang Yanyi
Prodigy 40 points
Part Number: TPA6304-Q1

Tool/software:

There is a derivative model of 26SA that needs to add SUBWOOFER. We use TPA6304 as the amplifier of SUBWOOFER. SUBWOOFER speaker only needs one Channel. The circuit is as the attachment:TPA6304-Q1.pdf

IC1200 for 4CH amp.

IC1205 for 1CH subwoofer amp.

My question as below

1.For 4CH amp, we need to change the input capacitor(C1236/C1240/C1241/C1242) from 0.47uF to 0.33uF for the audio quality improvement. So can the IN_REF capacitance change from 2.2uF to 1uF?

   Does the  input capacitor capacitance for 1CH  to the IN_REF capacitor capacitance need 1:4 ?

2.For 1CH subwoofer amp, we only use one Channel , If the input capacitor (C1255) capacitance to be 0.33uF, what is the capacitance of the C1388? 0.33uF ?

3.For 1CH subwoofer amp, There are three channels not used , their output load is open. So the FAULT pin will send out the low level to our SOC for  DC diagnostics.

How can we disable the three unused pin DC diagnostics?

Thanks!

  • +1
    TI__Mastermind 41890 points

    Hi

    Huang Yanyi said:

    1.For 4CH amp, we need to change the input capacitor(C1236/C1240/C1241/C1242) from 0.47uF to 0.33uF for the audio quality improvement. So can the IN_REF capacitance change from 2.2uF to 1uF?

       Does the  input capacitor capacitance for 1CH  to the IN_REF capacitor capacitance need 1:4 ?

    Yes, 1:4 is most suggested.

    Huang Yanyi said:
    2.For 1CH subwoofer amp, we only use one Channel , If the input capacitor (C1255) capacitance to be 0.33uF, what is the capacitance of the C1388? 0.33uF ?

    For unused channel, suggest to have same input capacitor and connect to GND. So still make the capacitance 1:4.

    Huang Yanyi said:
    3.For 1CH subwoofer amp, There are three channels not used , their output load is open. So the FAULT pin will send out the low level to our SOC for  DC diagnostics.

    Shouldn't be like that. As datasheet describes, Fault pin only react to below conditions. Could you please double check? By the way, DC fault means output contains a DC voltage which may damage speaker, different with DC diag.

  • +1 in reply to Shadow He
    Prodigy 40 points

    For question 1, Why it need 1:4 , Can you explain to us?

  • 0 in reply to Huang Yanyi
    TI__Mastermind 41890 points

    Hi 

     As below:

  • 0 in reply to Shadow He
    Prodigy 40 points

    Thank you very much.

    As the question 3, I will check it later, We will read out the register setting value when Fault happen.

    If I still have question, I will ask you again.

  • 0 in reply to Huang Yanyi
    Prodigy 40 points

    Hi Shadow :

    About the question 3, We need to confirm with you again.

    The attachment is the register setting of the subwoofer-amp.

    We can measure the fault signal output low and after we read it turn to high repeatedly at the current setting.

    And we also found that all the three unused Channels output the PWM signal, and the high level is about 1.8V.

    We set the unused Channel to be the Hi-Z, but it still output the PWM.

    Dose this cause the Fault pin output low?

  • 0 in reply to Huang Yanyi
    Prodigy 40 points

    TPA6304QDDVRQ1.xlsx

    Sorry, Forgot the attachment.

    Please help to check the register setting.

  • 0 in reply to Huang Yanyi
    TI__Mastermind 41890 points

    Hi Yanyi

    Huang Yanyi said:
    And we also found that all the three unused Channels output the PWM signal, and the high level is about 1.8V.

    It looks like the DC Load diag, but shouldn't happen on Hi-Z channels.

    For your Fault signal, also strange. When Fault pin goes low, means there's some fault happens, and the Fault pin won't go up by itself. Could you please check if you are keep clear fault? Reset? Or toggle STANBY pin?

    Read the register 0x10 to 0x13 during Fault pin goes low, check what is the fault been detected.

  • 0 in reply to Shadow He
    Prodigy 40 points

    hi Shadow, Thanks for your reply.

    After change the 0x4 to 51, the fault signal keeps low， and the unused channel had not the PWM output .

    But when we read the registers through I2C, the Fault can't be changed to high.

    the attachment is the value of the registers.

    Please help to check what error happen?

    two questions:

    1. 0x4 set to 51, but the 0xE value is 26, why not 06.

    2.why 0xD,0xE show that the" DC Load Diagnostic did not complete without faults on
    channel 1,2,4?

    sub amp register.xlsx

  • 0 in reply to Huang Yanyi
    TI__Mastermind 41890 points

    Hi Yanyi

    The behavior you described can't be explained. From your attached register value, it's quite possible your I2C has some problem. 

     Register 0x12 highest 2bits are not used, same as 0x14 highest 4bits. It's impossible you get these value, internally digital circuit is tied to 0, can't set to 1.

     Do you have EVM could used to do some test? It would easier for you to debug.