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Original question:

TLV320DAC3100: how to change the right-channel analog volume

TLV320DAC3100: Class-D output

Saxon Liw
Prodigy 80 points
Part Number: TLV320DAC3100
Other Parts Discussed in Thread: TLV320DAC32, TLV320DAC3101, TLV320AIC3262, TLV320AIC3263, TAS2521, TAS2505

Tool/software:

It looks like the mono Class-D can only take the Left Audio output. Is there a model of the same family of codec with a mono Class-D that takes the sum of L+R so that it is compatible with a stereo audio stream that could also go to a pair of stereo HP or line out at the same time?

Thanks.

  • 0
    TI__Expert 5030 points

    Hi,

    The TLV320DAC3100 has a configurable DAC output to the class-d amplifier output. Using page 0 register 63, you can set the left DAC output to be the sum of the left and right channel data, and then send that out the amplifier. The TLV320DAC3100 is our most powerful DAC with integrated amplifier + HP out, but you could check out the TLV320DAC3101 or TLV320DAC32 as other DACs with integrated amplifiers. 

    Let me know if you need more help with this!

    Best,
    Mir

  • 0 in reply to Mir Jeffres
    Prodigy 80 points

    Hi,

    I need to maintain a stereo output with the headphones out while having the class-D to output the L+R sum.

    Something which the obsoleted LM49352 was able to do very well. Can you reecommend a replacement part?

    Thank you.

    Best regards,
    Saxon

  • 0 in reply to Mir Jeffres
    Prodigy 80 points

    Also, the selection guide on the website does not help at all. So far, after searching through the list of possibe DACs and CODECs, it seems currently, only the TLC320AIC3263 has a mixer to output the sum of L+R to the Class-D.

    I need to maintain the stereo on the headphones and/or line out simultaneously.

  • 0 in reply to Saxon Liw
    TI__Expert 5030 points

    Hi Saxon,

    I see what you mean now, the 3100 does not allow for both a summed speaker out and a stereo headphone out. One way you might be able to get around this is sending the headphone stereo outs (voltage divided down to max .7Vrms) to two mic inputs and then routing the mic inputs to the amplifier without routing the left/right ins. This is a hacky solution, but would probably work if you were set on using a device from the TLV320AIC31xx line.

    The TLV320AIC3262 should work with your requirements, or the TLV320AIC3263. 

    Also, you could use any one of our two-stereo-output codecs/DACs connected to a small low power class D amplifier like the TAS2505 or TAS2521. 

    Let me know if you need more help with this.

    Best,
    Mir

  • 0 in reply to Mir Jeffres
    Prodigy 80 points

    Hi Mir,

    Thanks for the hint for the workaround on the TLV320DAC3100.

    It looks like the analog input specifications is not well documented in the TLV320DAC3100 datasheet. The headphones out is already specified at 0.707Vrms, so does this mean I can just channel the HPL abnd HPR directly into AIN1 and AIN2? Or do I need to AC couple them? If so, do I need to apply a DC bias on the AIN1 and AIN2? What is the input impedance for AIN1 and AIN2?

    The TLV320AIC3262 will not work because it is a stereo Class-D. I will need the TLV320AIC3263 with the mono class-D that can take sum of signals from both the L and R channels.

    BR,
    Saxon

  • 0 in reply to Saxon Liw
    TI__Expert 5030 points

    Hi Saxon,

    I wasn't sure if you meant to use headphone out or line out from the DAC. Headphone out is .707Vrms, but it says it is common mode at 1.65V. So, the output will be centered around 1.65V with a swing of .707Vrms, making the output range from .65V-2.65V. The absolute min/max analog input specification is from AVSS–0.3 to AVDD+0.3 V. This would be about 0-3.3V if you used the recommended AVDD voltage. So, the headphone out being sent to the inputs should be appropriate voltages for this to work, if HPVDD=AVDD. 

    You can use the techniques specified in this post to find the input impedance: https://e2e.ti.com/support/audio-group/audio/f/audio-forum/773059/faq-tlv320aic-codecs-how-do-i-calculate-the-input-impedance-of-an-tlv320aic-device

    Let me know if you need more help.

    Best,
    Mir

  • 0 in reply to Mir Jeffres
    Prodigy 80 points

    Hi Mir,

    The outputs will be configured as headphones out.

    Page 1 / Register 50 (0x32)  allows the connection of the AIN1/AIN2 to the CM. What is this CM, is it the same as the headphones out CM which is programmable via Page 1 / Register 31 (0x1F)?

    I will check if it is necessary to connect the HPL/HPR to AIN1/AIN2 through capacitors or I can just strap them directly.

    Thanks.

    BR,
    Saxon 

  • 0 in reply to Saxon Liw
    TI__Expert 5030 points

    Hi Saxon,

    This CM should be the same as the headphone out. You should be able to connect it directly since it has the same common mode voltage. For Page 1 register 50, you should set it to the input is "floating". The option to connect it to the common mode would bias a signal that was originally centered around 0V to have the correct common mode for the input, but your signal will already be biased. 

    Let me know if you need more help with this!

    Best,
    Mir