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TPA3255EVM: VDD and Reset Questions

RICK SIMON
Prodigy 150 points
Part Number: TPA3255EVM
Other Parts Discussed in Thread: TPA3255, , TPA3255-Q1

I have two more questions regarding the TPA3255 and TPA3255EVM.

1. The TPA3255EVM has a 12V regulator for VDD, but the datasheet shows an absolute max rating of 11.4V and typical of 10.6.  My circuit will have a 12V (out) DC-DC converter and to get a clean VDD, I was going to use a low-dropout linear regulator and regulate to 10.6V.  Can you explain why the EVM uses 12V and would it be better to regulate to 10.6V as I planned to do?

2. I'm not sure I fully understand the input side of the RESET control (U7 of the TPA3255EVM).  It looks like because of the low current draw they use a resistive divider to set the Vin to around 4V (slowed down by caps C84 and C67), but what exactly is the intention of the PVDD,  R6, C83, C84, intended to do?

Thanks,

Rick

  • 0
    TI__Mastermind 31380 points

    Hi Rick

    For Q1

      I'm a little confused about what you said, because in the datasheet, the typical value for VDD is 12V. Please check below table.

    For Q2:

      Seems not necessary devices, you can ignore them. 

  • 0 in reply to Shadow He
    Prodigy 150 points

    Dear Shadow,

    I think my confusion on the Q1 question is that I was looking at the data sheet of the the TPA3255-Q1.  Please see the attached specs with lower Vdd.  In my case I have a 12V output DC-DC converter that is used to power a single-board computer along with other things.  It would be nice if I could use that same converter output (perhaps isolated by a ferrite bead) for the Vdd voltages as well.  If  a cleaner linear regulator is needed please tell me the main differences in functionality and availability of the TPA3255-Q1 vs. the TPA3255DDV.

    Thanks,

    Rick

  • +1 in reply to RICK SIMON
    TI__Mastermind 31380 points

    Hi Rick

         The Q version is produced on another product line, using different process. The main difference is on the working voltage range, you need to follow closely to the datasheet. The function should be no difference.

         Sorry no detailed comparison table about these two devices.

  • 0 in reply to Shadow He
    Prodigy 150 points

    Dear Shadow,

    It seems like the TPA3255DDV is more common and easier to get (please confirm that if you can).  Assuming that is the part I use, please advise on the other question regarding Vdd.  In my case I have a 12V output DC-DC converter that is used to power a single-board computer along with other things.  It would be nice if I could use that same converter output (perhaps isolated by a ferrite bead) for the Vdd voltages as well.  If  a cleaner linear regulator is needed please explain why?

    Thanks,

    Rick

  • 0 in reply to RICK SIMON
    TI__Mastermind 31380 points

    Hi Rick

       Yes, 12V is more commonly used.

       Please make sure the 12V voltage at VDD pin is within the recommend operating condition, 10.8V to 13.2V. You can try put a LC filter like EVM, or only large capacitor (like 470uF) + 100nF like datasheet page 26 to reduce the ripple.