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Original question:

TPA3123D2: Part overheats at power-On

TPA3123D2: Part overheats at power-On

Namith HL
Intellectual 570 points
Part Number: TPA3123D2
Other Parts Discussed in Thread: TPA3118D2, TLV431

Hi,

we are using TPA3123D2 chip for our current design, we are referring TPA3123D2 evaluation model as the design reference .

May i know the reason behind using 4.7K ohm resistor across each ROUT and LOUT wrt to AGND.

As our understanding these two resistor work as a minimum load to the amplifier? Is it correct?

Note:we are facing heating issue of the amplifier for very less duration, Since we have missed 4.7KOhm across the two channel, after fixing these two resistor we have reduced the heating issue.

Regards,

Namith

  • 0
    TI__Mastermind 24835 points
    Hi Namith,
    The 4.7kOhm resistors are bleeder Resistor for Single-Ended Output Capacitor, and the different value means different discharge time of the large output capacitor.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Intellectual 570 points

    Hi,

    we have facing heating issue of the chip during power on reset of the board.

    In normal operation its working fine , but once restart  the supply its taking more current and chip getting more heat. can u suggest us hoe to resolve this issue.

    Note: we are not using 470uF for PVCCL decoupling we are using 6800uF for the PVCCL for the surge protection.

    Regards,

    Namith

  • 0 in reply to Namith HL
    TI__Mastermind 24835 points
    Hi Namith,
    Could you please let me know whether the issue is still there when toggling SD? Or only when recycling power supply?
    Please show us your SCH, it would be helpful for our debug work.
    Did you try with 470uF caps instead of 6800uF for VCC decoupling on the baord? Is the issue still there?
    BTW, this product is quite old and the design support could be limited. Please refer to TPA3118D2 which can be used to replace TPA3123D2.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Intellectual 570 points

    Hi,

    Attached is the schematic for our amplifier design using TPA3123D2.Kindly review the schematic and give us the feedback.

    Regards,

    NamithTPA3123D2 Amplifier design for TI REVIEW.pdf

  • 0 in reply to Namith HL
    TI__Mastermind 24835 points
    Hi Namith,
    How many boards did you test? Does the issue occur on all of the boards or some of them? How much is the percentage?
    What if you populate the R256 and R257 on the output? Does it help? As I mentioned above the two resistors have to be populated as the bleeder resistor for single-ended output capacitor. In addition, the large cap on the VCC also needs to be charged during power-up. What if you use a lower one?
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Intellectual 570 points

    Hi Shawn,

    • we have tested almost 4 assembled board till now,all are having the same heating issue.
    • R256 and R257 also kept and tested issue remains same.

      our customer have tested same amplifier output with the POE output 24V. They have witnessed folloowing results.

      Reservoir storage

      This shows the effects of a 180uH and 10,000uF filter (energy storage) between the supply and the amplifier.

      The yellow trace is the output voltage (pink-noise) the green trace is the current.

      The first picture is without the filter, the second is with the filter.

      Unsurprisingly it can be seen that the higher frequency > 100Hz spikes are reduced.

      In practice this made little difference to the point at which the PoE Injector cut-off, but reduced dips in the 24V due to the PoE supply itself current limiting.

      As this reason we have removed two 470uF capacitor at the decoupling side as already there is on large reservoir cap 6800uF available.

      I have seen same heating issue in the Ti forum faced by others , but there is no conclusion for resolve this issue,Please give us the any suggestion to resolve the issue.

      Regards,

      Namith

  • 0 in reply to Namith HL
    TI__Mastermind 24835 points

    Hi Namith,
    May I know where is the heat from? From AMP or inductors or other components? We know that some customer had the similar heat issue previously, and the root cause is the caps failure on the board. Please help to check the component failure/wrong assembling on the board.
    I saw there is a de-pop circuit in the SCH. To exclude the possiblity of the issue here, could you please remove the resistor R237 and R238 to see if there is any improvement?
    How much is the rated current of the inductors in the output filter? Make sure they are higher than the max through current and enough margin is reserved.
    Please also bypass the sensing resistor on the power supply and output to excluding any  potiential issue caused here.
    And we know there is application limitation for SDZ opertion on TPA3123D2, please make sure it's followed.

    Hold time on SDZ TPA312xD2.doc
    Best regards,
    Shawn Zheng

  • 0 in reply to Shawn Zheng
    Intellectual 570 points

    Hi shawn,

    As per your suggestion we have isolated the depop circuit by removing R237 ,we have found the there is no heating issue.

    Kindly give us any solution for this as we want depop circuitry for our application . now we are getting the depop sound during the power on/off time.

    Regards,

    Namith

  • 0 in reply to Namith HL
    TI__Mastermind 24835 points
    Hi Namith,
    We can't replicate this issue with the TPA3123D2 EVM. Could you please try with the same setup with the EVM to see if the issue is still there? And let's use a power supply instrument at first.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Intellectual 570 points
    Hi,

    For Depop circuit there is divider network for TLV431 regulator ,may i know the value for 24V supply.

    For the TLV431 used required 1.24 reference voltage , but as per divider we set divide into 2.5V ref. does it affect the heating issue since i have spoken about this issue.

    If we isolate the depop circuit heating does come out.

    Can u please explain about the depop circuit working and also about Divider circuit also

    Regards,
    Namith
  • 0 in reply to Namith HL
    TI__Mastermind 24835 points
    Hi Namith,
    The wrong reference voltage could cause some unexcepted issue. And with very high VCC, the power consumption on the resistor R239 could be very high. The depop is optional, and it't actually not necessary as long as there is no pop noise issue. Please find the explanation about how this circuit works on the page 4 in the EVM user's guide: www.ti.com/.../slou208.pdf
    Best regards,
    Shawn Zheng