TAS5630 abnormal failure

Hello,

Can anybody help me?

I have made one PCB for TAS5630DKD testing, using all TI recomended layout. I also have added to my board one preamplifier to filter the audio input signal (Low pass and high pass). The TAS5630 stage is powered by +49V DC (PVDD) and +12V by an 7812 regulator for GVDD supply, and my preamplifier is supplied by +/-15V simmetric supply.

A problem was occurred, result in failure of TAS5630 chip (i have burned about five chips in my tests), when I plug the audio signal cable on the RCA jack of preamplifier with the TAS5630 active (READY). I know, in this condition one large transient is generated - in another amps, also in TAS5630PHD evaluation board this generate a great POP noise into speaker, but in my board this action results in a chip failure.

The problem occur also when I disconnect the preamplifier output from TAS5630 amp and insert the audio signal direct into inputs (by electrolytic capacitor and 100R resistor as recommended) - Any transient generated by cable "plug and unplug" when the chip is active (READY) causes a serious failure of TAS5630...

Regards,

Paulo

  • In reply to SteveCrump:

    Steve, is there any reason not to design for X7R surface-mount ceramic (non-polar) input capacitors? They are available in 1206 and 1210 sizes and seem reasonably priced.

    Russ

  • In reply to Russell May:

    Russell,

    X7R caps contribute to THD at low frequencies. the TAS5630 is high performing enough that you see a difference between ceramic and electrolytic. So, we use electrolytic on the EVM. if you're not as concerned with THD, then ceramics are fine.

    -d2

  • In reply to Don Dapkus:

    Thanks for reminding me of the distortion differences. Can you reference any objective distortion comparisons between 10uF X7R caps and tantalum caps at low frequency? The only similar comparison I have seen is at http://industrial.panasonic.com/ww/i_e/21088/smd-film-capacitor_e/smd-film-capacitor_e/data/02.html. It shows that 1uF X7R caps have less distortion than 1uF tantalum caps at about 400Hz or less. Above 400Hz, the tantalum caps are better. 50 to 400Hz is the frequency range that I am interested in, but I don't know how different the results would be for 10uF caps and TAS5630 input loads in PBTL mode.

    Another thing I wonder about is leakage. I am pretty much stuck with using 16V 1206-size caps for now. Tantalum leakage rating (for Kemet T491A106K016AT) is equivalent to about 8Megohms at 20 degrees C. 10uF X7R leakage rating can be much better (100Megohms for AVX, 50Megohms for Kemet, but only 5Megohms for Murata, for examples). With about 4VDC of bias, the AVX X7R caps could be expected to have up to about 0.50-0.04=0.46uA less leakage than these tantalum caps. That could lower the TAS5630 output voltages by about 0.23VDC at room temperature. DC output voltages of all of the several EVM's I have, are a little less than half of their 48VDC supply. Lower input capacitor leakage should raise their DC outputs closer to half of the power supply voltage, which might allow slightly higher symmetrical output voltage swings.

    Russ