• State TI Thinks Resolved
  • Locked Locked
  • Replies 9 replies
  • Answers 2 answers
  • Subscribers 30 subscribers
  • Views 2336 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.

TPA 3123 high shutdown current

Mihai Niculescu Oglinzanu
Prodigy 60 points

Other Parts Discussed in Thread: TPA3123D2

Hello;

I`m starting to do builds with many of your classD amplifiers (tpa -tas)

But for TDA3123D i had encountered a big issue;

In shut down mode (SD to low) the chip is consuming very much:

VCC-12v - 80mA in shut down

VCC-20V - 100mA in shut down

VCC-28V - 120mA in shut down

in idle with no input signal nonmuted the chip is consuming between 20-50mA

Mute pin is hardwire to low (always unmuted); sd pin is upped to vcc with 100kR

I have done 3 build until now and all of them have the bug.

Other build of my own (tpa 3106) don`t have this problem.

This is pretty fail in my book.

  • 0
    Prodigy 60 points

    Anyone have the evaluation board for this chip to run some simple tests?

  • 0 in reply to Mihai Niculescu Oglinzanu
    TI__Expert 5000 points
    Hi, Mihai
    I have checked with TPA3123D2's EVM board, the shutdown current is lower than 1mA, and the quiescent supply current with out shutdown （PVCC=16V）is 22mA. Maybe there has some issue in your board.
  • 0 in reply to Peter Cao
    Prodigy 60 points

    OK; i solved the enigma!

    In my pcb the gain is hardwire to max (36db)

    that means i have 9kR input impendance> and because of that; i used 10uF input caps - for having linear response down to 20HZ (cut is on 2HZ - -3db)

    Now, because o have used 10uF on input cap; i also used 10uF on bypass ; according to datasheet (the start up rate to avoid pop-up)

    Now: from my measurements, when i power up the tpa (sd high -  normal operation) for some seconds ; amp is mute but the supply current is ~ 100mA !; after the start of tpa (normal operation) the supply current is back to 20mA. Now, if i i put sd low (shut down) the tpa will shut down but for 7 seconds supply current is again100mA!; and after 7 seconds supply current will drop indeed to 1 mA. this test was done with 16V.

    For 28V VCC the shut down high current consume(100mA)  will last 14 seconds ; and after that will drop below 1mA .... 

    SO; for large bypass capacitor ; the startup-shutdown current will be big (~100mA) for some several seconds;

    I need a designer engineer to explain me what part from TPA will consume this much on startup-shutdown (the time when bypass capacitor is charged-discharged; My guess is that the supply reference circuit will drain this much current in  chargeup-discharge sequence with some internal resitors but i need to be sure that long time shut down current (14 seconds with 100mA for 28V supply will not destroy some internal regulators...)

  • 0 in reply to Mihai Niculescu Oglinzanu
    TI__Expert 5000 points
    Hi, Mihai
    Glad to hear you that you have solved the enigma! But I think your board still has some issues which I think not make sense. Can you share your schematic and I will review it later.
  • 0 in reply to Peter Cao
    Prodigy 60 points

    The board as you see in first picture is very simple and basic; and nothing can go wrong with that... after all the amp is working fine; except the shutdown issue.

    The schematic is basically identical to datasheet; except gain control pins and the mute pine are hardwire; to vcc and gnd;

    Can you replace the bypass capacitor on evm board with 10uF or greater? and then do same tests?

  • 0 in reply to Mihai Niculescu Oglinzanu
    TI__Expert 5000 points

    HI, Mihai

          Yes, it make sense. The BYPASS is the reference for pre-amplifier input. Also controls star-up time via external capacitor. If you increase the capacitor, internal circuit of TPA3125D will guarantee the reference voltage until it increase to a proper level as the datasheet says. You can find that at the beginning of the start up, the PWM duty cycle is not 50% (normal state should be 50%), it is because the reference voltage of pre-amplifier is still lower than normal. Suggest you  use 1uF as the BYPASS pin capacitor.

         TPA3123 start & shutdown.pptx

  • 0 in reply to Peter Cao
    TI__Expert 5000 points

    Hi, Mihai

        You can find the attachment which I send in the former post.

  • 0 in reply to Peter Cao
    Prodigy 60 points

    ok now; this is normal behavior;

    i have already start to decrease the bypass capacitor to the point of avoiding  the pop up as much as possible due to high input caps; and i don`t want to redesign the pcb because already made 50 of them.

    thank you for the last tests :D ; and clarifying  the issue;

    Anyway, maybe you should suggest to the team to make a new revision for the datasheet in where the bypass section to be more explicative like this thread :) 

    Moving now to other builds (i have a plenty of them)

  • 0 in reply to Mihai Niculescu Oglinzanu
    TI__Expert 5000 points
    Hi, Mihai
    Thank your for your interesting for so many TI audio device and thanks for your suggestion about the datasheet, it is very meaningful.