• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 30 subscribers
  • Views 154 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

TPA6120A2: Stops functioning after short period

James Boulton
Prodigy 10 points
Part Number: TPA6120A2
Other Parts Discussed in Thread: TPS61093

I'm using a TPA6120A2RGYT as a headphone audio amplifier. The application is battery powered and I have a TPS61093DSKR generating +/-12V for the amplifier.

I've prototyped the amplifier section using a TPA6120A2 module and separate boost converter module, this combination has been working fine, albeit with a different boost controller. On the PCB version of this prototype I am able to get good, clear audio for about 8 seconds then it starts to distort and then mostly stops being amplified apart from blips which correspond to beats in the audio. The amplifier is currently configured as 2V/V gain, although I had previously had it configured at 3V/V with the same results.

Initially I thought the boost regulator was failing to deliver enough current, but the voltage is stable at around +/-12V with minimal ripple. To rule out the boost controller I replaced the +/-12V generated by the TPS61093 by the separate boost module I had used to prototype. Exactly the same result.

Another thing which occurs is increasing current draw from the +/-12V boost controller, gradually increasing in speed until the distortion kicks in and then stabilises. This is with headphones connected. When headphones are not connected there is no current increase, however if headphones are plugged in after the period the audio distorts, the distortion is present

I had assumed a heat dissipation issue, but the TPA6120A2 remains cold to the touch as do all capacitors. I am using 4.7uf (by the boost converter) and 10uf on the positive and negative rails and 100nf per input pin. I have also tried using an additional 100uf elctrolytic on each rail with no change.

When using an external boost converter if I quickly power cycle it the audio will remain clean again for a similar period to turning the device on.

This is the schematic for the 3V/V gain originally tested. 

Any thoughts on what could be causing this would be appreciated.

  • 0
    Prodigy 10 points

    Quick addendum. I've noticed if I squeeze the TPA6120A2 from top and underneath of the PCB then it will continue to play audio fine and does get quite warm. If I just press from the top of the of the board with an implement, no difference. So it's looking like it may be a poorly soldered pad and I think my finger and thumb may be enough of a heat sink to allow it to function.

  • 0 in reply to James Boulton
    TI__Genius 14341 points

    Hello James,

    Please keep me updated on if you need additional support.  If you have trouble or find that good soldering & rework does not resolved your issue, please let me know.

    Best,

    Alec

  • 0 in reply to Alec Saebeler
    Prodigy 10 points

    After mashing my thumb around the PCB with a little more precision, I found the issue was not with heat, but gain. This ties up with what I was seeing on the output -- as the distortion kicked in the output drifted toward 10V and stayed there.

    Not paying enough attention to the datasheet and example schematics I AC coupled the audio input which I think lead to instability in the gain, eventually leading to the failure I was seeing. Direct coupling with the 50R on input and it's working fine.