• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 30 subscribers
  • Views 128 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.

PCM3168A: PCM3168A running hot

Scott A Miller
Prodigy 80 points
Part Number: PCM3168A


Tool/software:

I'm testing out a prototype multi-channel audio interface that uses the PCM3168A, and the IC seems to be running awfully hot - I'm trying to figure out if this is normal (the datasheet does give a power dissipation figure of around 1200 mW) or if I've fried this one. I likely killed at least one IC when a connector ripped loose and left a DC-DC converter on the board floating and I'm out of spares to try for a couple of days.

If I put my finger on it, it feels like the temperature is cycling and it gets hot enough at times that I can't keep my finger on it. I'd give numbers but of the three thermal cameras at my disposal two won't power up and the other is no good at close range.

The board I'm working with is a simplified one to make it easier to isolate the codec issues than on the full board so only one input and one output channel are connected. The other VINs and VOUTs are floating but aside from that I don't see any connection issues. This prototype is only a 2-layer board but the thermal pad is connected to the bottom layer ground pour with 36 vias. Can anyone tell me what a normal temperature for this IC is?

Thanks,

Scott

  • 0
    TI__Mastermind 48205 points

    Hi Scott,

    By default all the converters are powered up once power is given to the codec, so even if there is no connection, those converters are working. ~45C is where things become too hot to touch, and the codec is still healthy up to 85C so that's not an immediate indicator of a problem. I would check what kind of current you are pulling into the power supplies. You can double check against some of the numbers on page 12 of the datasheet. That will give a better picture if something has become damaged or not.

    Best regards,
    Jeff McPherson

  • 0 in reply to Jeff McPherson
    Prodigy 80 points

    I figured the converters would be running, I just wanted to be sure that having the inputs and outputs not properly terminated wasn't going to cause crazy power consumption. Approximating the maximum load of six channels in operation is a good thing as far as my testing goes.

    The board draws 190-200 mA fully powered up. I pulled the MCU's clock crystal as a quick test and power consumption dropped to near zero, so it's not a connection issue. I put the crystal back in and disconnected SCKI and I get 20-30 mA (about right for an idle MCU) and no heat from the codec. This seems in line with the typical supply current shown on page 12. So that all seems OK - I'll keep testing and I have spares coming in tomorrow.

    Can you tell me if the PCM3168A can be used with MLCCs or tantalum caps in place of the 10 uF aluminum electrolytic caps? Vertical space is limited on this board. It's not a high fidelity application, just voice band at 16 kHz and it's getting quantized down to 8 bits so a bit of extra noise doesn't bother me but I don't want to cause an internal LDO to start oscillating or something.

    Thanks,

    Scott

  • 0 in reply to Scott A Miller
    TI__Mastermind 48205 points

    Hi Scott,

    Unfortunately the LDOs do need the higher ESR from electrolytic caps. It's not really related to audio performance. You're welcome to use ceramic caps elsewhere such as in the audio signal chain. I also checked the reference boards and they use the recommended 10uF electrolytic caps so you're best off using those caps for the VCOM/VREF pins.

    Best regards,
    Jeff McPherson

  • 0 in reply to Jeff McPherson
    Prodigy 80 points

    I was thinking that might be the case. Not a huge deal for this project; I'll find room.

    Thanks,

    Scott