• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 30 subscribers
  • Views 352 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TLV320AIC24K Drive 500ohm headphones

Michael Brantley
Intellectual 1535 points
Other Parts Discussed in Thread: TLV320AIC24K

Audio geniuses,

Is there any way we can use the TLV320AIC24K to drive 500ohm headphones from the 150ohm HDSO output pins? 

Thanks,

Michael

  • 0
    TI__Genius 9430 points

    Hey Michael,

    Yes, the HDSO output can drive a 500 ohm headphone. The reason the datasheet states that it drives 150 ohm loads is to show the lowest impedance the device can handle. With lower impedance loads (also sometimes confusingly referred to as higher loads), the current is higher. Anything below 150 ohms would require a current that exceeds what the device was designed for. Anything with higher impedance than 150 ohms is okay because the current will be below the maximum.

    A couple of points that would be worth thinking about when using this speaker output for headphone output:

    1) This output is differential (a positive and negative signal 180 degrees out of phase), headphones are typically single-ended (1 single line and a ground). Many have been tempted to apply the negative signal line to the ground of a headphone, this works for conventional headphones (they are just small speakers) but if a user connects active headphones (i.e. with noise cancelation) or uses a powered docking station that expects the ground to be ground, this could cause some issues. I don't see why just using the positive signal and then grounding the headphone wouldn't work.

    2) This is a mono output. Headphones are usually stereo. To get stereo you would need to use another output (like HNSO)

    Please let me know if you have any more questions,

    Nate

  • 0 in reply to Nate Enos
    TI__Intellectual 1535 points

    Thanks Nate. 

    If we use the HNSO+/- outputs, will this work on headphones? I am not sure if the headphones are single-ended or fully differential. 

  • 0 in reply to Michael Brantley
    TI__Genius 9430 points

    It will work as long as it's done correctly. The headphones will be single ended. The differential outputs will have DC offset and that will need to be filtered with a DC blocking cap if used for a headphone.

    Basically the options would be mono 1) use just single HNSO differential output and put the positive (HNSO+) signal through a DC blocking cap and then to one channel of the headphone. Then use the negative signal (HNSO-) and run that rhough a DC blocking cap and then to the other channel of the headphone. You then ground the headphone ground and you will get a mono output from a single differential output. This is a viable solution but DC block caps will need to be a large value to get a good frequency response and will drive up the size and cost of the BOM. Also, it's worth mentioning that the outputs will be 180 degrees out of phase. The human ear can't hear constant phases so for headphones you wouldn't notice, but if this was used for two speakers the out of phase signals would create some odd nodes. So make sure this is just being used for headphones.

    The alternative is for stereo  2) Use two differential outputs, such as HNSO and HDSO and just use the positive (HNSO+ and HDSO+) to go to the headphones. You will still need DC block caps as before but this lets the headphones have stereo sound and you get rid of the phase issue.

    The most important thing to consider is why use the AIC24K?

    If you notice on ti.com this device does not have an EVM. This is because this part is maturing and the EVM has been discontinued. We only recommend using this device for existing projects or for customers who have experience with this part. For new projects I suggest something in the AIC3xxx range.

    If you are having any issues meeting the specifications of a project or any further questions please let me know,

    Nate

  • 0 in reply to Nate Enos
    TI__Intellectual 1535 points

    Thanks Nate.

    This part has been used in previous designs, and we are trying to figure out the viability of reusing it for our current project. 

    Michael